Geology of the southeast end of the Paleozoic portionof the Canelo Hills, Santa Cruz County, Arizona

Item Type text; Thesis-Reproduction (electronic); maps

Authors Denney, Phillip Paul, 1939-

Publisher The University of Arizona.

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GEOLOGY OF THE SOUTHEAST END OF THE PALEOZOIC PORTION

OF THE CANELO HILLS, SANTA CRUZ COUNTY, ARIZONA

byPhillip Paul Denney

A Thesis Submitted to the Faculty of theDEPARTMENT OF GEOLOGY

In Partial Fulfillment of the Requirements For the Degree ofMASTER OF SCIENCE

In the Graduate CollegeTHE UNIVERSITY OF ARIZONA

1 9 6 8

STATEMENT BY AUTHOR

This thesis has been submitted in partial fulfill­ment of requirements for an advanced degree at the University of Arizona and is deposited in the University Library to be made available to borrowers under rules of the Library.

Brief quotations from this thesis are allowable without special permission, provided that accurate acknow­ledgment of source is made. Requests for permission for extended quotation from or reproduction of this manuscript in whole or in part may be granted by the head of the major department or the Dean of the Graduate College when in his judgment the proposed use of the material is in the interests of scholarship. In all other instances, however, permission must be obtained from the author.

SIGNED: y „ /

APPROVAL BY THESIS DIRECTOR This thesis has been approved on the date shown below:

fyilihd J)> ,%2— 0cf. 2. I?6’7W. D. Wf Dite '

Professor of Geology

ACKNOWLEDGMENTS

Many individuals have assisted the author during the preparation of this thesis. I wish to take this oppor tunity to thank as a group those fellow graduate students whose informal comments suggested new approaches for studying specific problems or brought forth new lines of thought.

Additionally, I would like to thank Dr. D . L. Bryant and fellow student A1 Reid for the identification of many fossils and Turgut Cetinay who first introduced me to the Lower Paleozoic section in the Canelo Hills.

I wish to specifically acknowledge the great help given by Dr. Andrew Nevin of the Phelps-Dodge Corpora tion who has read and critized parts of this manuscript. Thanks are also extended to others at the Phelps-Dodge Corporation for loaning otherwise unattainable material to the author.

The Tucson sub-office of the IBM Corporation graciously allowed the author’s wife, an employee of the company, many hours of use of the new Magnetic Tape Selectric Typewriter on which the manuscript was prepared.

iii

ivFinally I offer my most sincere thanks to my wife,

Dorene. Her efforts for the past five years have made this thesis possible.

Tne help of many people is acknowledged; however, the inferences and conclusions contained in this thesis are the author's, and he accepts full responsibility for them.

TABLE OF CONTENTS

PageLIST OF ILLUSTRATIONS............................viiLIST OF TABLES...................................viiiLIST OF PLATES..................................... ixABSTRACT........................................ x

1. INTRODUCTION.................................... 1Purpose .................................... 1Location and Accessibility.................. 2Physiography................................ 2

Regional Setting........................ 2Local Features.......................... 4Drainage................................ 5

Previous W o r k .............................. 5Field and Laboratory W o r k .................. 6

2. GENERAL GEOLOGY ................................ 83. PALEOZOIC STRATIGRAPHY.............................11

Cambrian System-Abrigo Limestone...............11Pre-Devonian Unconformity .................. 14Devonian System-Martin Formation...............14Mississippian System-Escabrosa Limestone. . . 17Post-Escabrosa Disconformity...................21Pennsylvanian and Permian Systems .......... 23

Naco Group................................. 23Horquilla Limestone ................ 23Earp Formation.........................25Colina Limestone.......................31Scherrer Formation.....................33Concha Limestone.......................36

4. MESOZOIC AND CENOZOIC STRATIGRAPHY.................37Mesozoic rocks.................................37Triassic and Jurassic Systems .............. 38

Canelo Hills Volcanics.....................38Name and Distribution.................38Lithology.............................38Thickness.............................41Age and Correlation...................41Environment of Deposition .......... 43

v

viTABLE OF CONTENTS--Continued

PageCretaceous System-Bisbee Group............ 47Cenozoic Sedimentary and Volcanic Rocks . . 48Cretaceous-Tertiary Dike.................. 49

5. STRUCTURAL GEOLOGY............................ 51Folds.................................... 51Early Faulting............................ 55

Dam Fault . ........................... 56Faults in the Earp Formation.......... 57Burro Fault.......................... 59Smoke Mountain Fault.................. 61

East to West Striking Faults.............. 62Late Northeast Striking Faults............ 63

Western Canyon fault.................. 64Exotic Blocks ............................ 65Regional Implications of the Exotic Blocks. 67Late Gravity Slide........................ 69

6. SUMMARY............ 70APPENDIX I. . ................................. 72APPENDIX I I .................................. 76

Section 1 ................................ 77Measured Section of the Abrigo Limestone 77

Section 2 ................................ 80Measured section of the Martin Formation 80

Section 3 ................................ 86Measured section of the Escabrosa

Limestone........................ 86Section 4 ................................ 94

Measured section of the Earp Formation. 94Section 5 ................................ 98

Measured section of the Canelo HillsVolcanics........................ 98

APPENDIX III..................................... 103Fauna of the Naco Group within the

East-Central Canelo Hills ............ 103REFERENCES....................................... 104

LIST OF ILLUSTRATIONS

1. Index map showing the location of the thesis area in eastern Santa Cruz County,Arizona .................................. 3

2. El Diagram for the Abrigo Limestone . . . . 133. Slightly irregular contact between Abrigo

Limestone on the right and Martin Formation 154. El Diagram for the Martin Limestone . . . . 185. Photo mosaic of Escabrosa Hill. . . . . . . 196. El Diagram for the Escabrosa Limestone. . . 227. Horquilla Limestone containing Chaetetes

Favosus, field guide to Horquilla Limestone 268. Faulted outcrop of the chert-pebble conglo­

merate of the Earp Formation.............. 289. Block of ripple-marked, orange-weathering

dolomite of the Earp Formation............ 3010. Cross-bedding in Scherrer sandstone; gravity

slide block.............................. 3511. Photo mosaic showing the Manzanita Block

of Paleozoic limestone interbedded in the Canelo Hills Volcanics.................... 40

12. Lochiel Road block........................ 4213. Proposed Correlation of the Canelo Hills

Volcanics................................ 4514. Vertical flow banding in Smoke Mountain Dike 5015. Corral Fault.............................. 53

Figure Page

vii

LIST OF TABLES

1. Classification of Carbonate Rocks ........ 732. Energy Index Classification of Limestones . 743. Classification of Thickness of Stratification

Units.................................... 75

Table Page

viii

LIST OF PLATES

Plate1. Geologic Map of the East-Central Canelo

Hills, Santa Cruz County, Arizona. in pocket2 Geologic Cross-Sections of the East-

Central Canelo Hills. in pocket

ix

ABSTRACT

The central Canelo Hills were formed by the block faulting and tilting of Paleozoic and Mesozoic sediments. This fault block trends N3lPw and dips 3£PSW. Beginning with the Upper Cambrian Abrigo Limestone, the rocks exposed are progressively younger from northeast to south­west. The Canelo Hills Volcanics, a group of interbedded sediments, lava flows, and welded tuffs, are in fault contact with the Paleozoic limestones along the southwest side of the fault block.

The Canelo Hills Volcanics are the first volcanic and sedimentary rocks in southeastern Arizona that can be definitely ascribed to the Lower Mesozoic. Their presence may necessitate the reappraisal of some of the "Cretaceous (?)" rocks in nearby areas. In addition, the presence of exotic blocks of Paleozoic limestone interbedded in the lower part of the Canelo Hills Volcanics suggests an alter­nate hypothesis to account for an anomalous contact between Paleozoic and Mesozoic rocks in the Canelo Hills. Others have considered this contact to be a low-angle thrust fault; this paper suggests that the contact is no more than an unconformity or at most a normal fault.

x

xiTilting of the Canelo Hills block probably

resulted in two sets of steeply dipping normal faults.The older of these two sets is composed of strike faults and the younger is cross faults. Both sets are believed to have followed anisotropic directions in the rocks.

The only folds present in the area are drag folds developed adjacent to faults. The presence of reverse drag along the downthrown side of some faults suggests that the fault planes may be curved at depth.

CHAPTER 1

INTRODUCTION

The central portion of the Canelo Hills is typical of the Basin and Range block faulting so well displayed elsewhere in the Basin and Range Province of the western United States. During late Mesozoic or Tertiary time, pre-existing strata in the area was upfaulted and tilted to the southwest in response to vertically acting forces.The structures that developed during this block faulting are the topic of this thesis.

PurposeFor many years southern Arizona has been fertile

ground for those interested in the study of compressional tectonics. This concentration on compressional structures such as thrust faults has lead to a general neglect of vertical tectonics in a region where the latter predominate.

The immediate goal of this thesis is to determine structural relationships among the rocks exposed in the central Canelo Hills. It is believed that the system of tectonic and sedimentary structures existing there will reveal the importance of block faulting and necessitate a re-evaluation of some compressional theories presently existing for the area.

1

2Location and Accessibility

The area covered by this report is centered 54 miles south-southeast of Tucson and 26 miles east-northeast of Nogales (Fig. 1). It is bordered on the south and west by the main range of the Canelo Hills and on the east by the Canelo-Lochiel road. The area includes all or part of sections 12, 13, and 24 of T 22 S, R 17 E, and all or parts of sections 7, 8, 17, 18, and 19 of T 22 S, R 18 E, Gila and Salt River Baseline and Meridian. The area of study lies entirely within the Coronado National Forest and is located on the O ’Donnell Canyon 7.5 minute topographic map of the U. S. Geological Survey.

From Tucson, the area is reached by following high­ways U.S. 80 and Arizona 83. Jeep trails lead off the Canelo-Lochiel road (Arizona 83) providing access into the back country. Most roads may be traversed by car except during the summer rainy season.

PhysiographyRegional Setting

Arizona has been divided into three physiographic provinces (Ransome, 1904, p. 1 ): the plateau region inthe northeastern part of the state, the desert region in the southwest, and the intervening mountain region. The Basin and Range Province in Arizona approximates the area of the desert and mountain physiographic provinces.

TUCSON

Scale

Miles PantanoM oun tain View

P I M A CO.____r SANTA C R U Z CO.

Amado

Sonotia

E l g i n

PatagoniCanelo

Thesis area

NOGALES

Fig. 1. Index map showing the location of the thesis area in eastern Santa Cruz County, Arizona.

4

Two major structural divisions have been recognized by Wilson and Moore (1959, p. 90). These are the Plateau province in the northern and the Basin and Range province in the southern part of Arizona. Separating the two prov­inces is a transition zone in the central and southeastern parts of Arizona.

The Basin and Range province is characterized by short, subparallel, block faulted ranges of which the Canelo Hills is an example. Separating the ranges are intermontane valleys formed by downfaulted blocks buried beneath alluvium.

Local FeaturesThe Canelo Hills form a topographic barrier that

separates the intermontane valley existing between the Patagonia Mountains on the west and the Huachuca Mountains on the east. This divide extends 30 miles from the south­west side of the Huachuca Mountains to the southern foot­hills of the Santa Rita Mountains. The main range of the Hills trends N45°W and is commonly steeper on the western side. Slopes in this terrain frequently exceed 1,000 feet per mile and locally approach 1,500 feet per mile. Four prominent peaks exist along the crest of the main ridge:Mt. Hughes (5,861 feet) at the northern end, Canelo Peak (6,110 feet) within the thesis area, Lookout Knob (6,171 feet) just south of Canelo Pass, and Lone Mountain

5(6,475 feet) at the southern extremity of the Hills. The crest of the Canelo Hills is held up by resistant rhyolite flows and sedimentary rocks that form a steep western dip slope. On the eastern side of this main range, a group of lower "secondary hills" composed mainly of Paleozoic lime­stones parallel the main trend.

DrainageAll streams in the area are intermittent and flow

only after the summer rains begin. The western slopes of the Canelo Hills are drained by Sonoita Creek which flows to the southwest into the Santa Cruz River and thence to the south into Mexico. The eastern side of the Canelo Hills drains either into the Babocomari River that flows east­ward to the San Pedro River or into Cienga Creek which eventually reaches the Santa Cruz River near Tucson. As a result of its steeper gradient, Cienga Creek is today beheading the headwaters of the Babocomari River a few miles north of the area mapped.

Previous WorkSchrader and Hill (1915) , in a geologic reconnais­

sance of south-central Arizona, briefly examined the Canelo Hills and described some of the general aspects of geology there. The first detailed work, however, was in 1947 when Feth mapped the north end of the Hills. In that area,

6Feth mapped what he believed to be a block of Permian limestone thrust to the southwest onto Cretaceous (?) sedimentary and Tertiary volcanic rocks. This view has been held to the present day.

Bryant (1955) , in a reconnaissance visit to the Hills, measured the thickness of some of the Permian rocks and added to the known stratigraphy of the area.

Cetinay (1967) was the most recent investigator in the Canelo Hills. He mapped the central portion of the central Canelo Hills block and described a thrust of Paleozoic strata to the northeast onto Cretaceous (?) deposits.

Hayes, Simmons, and Raup (1965, 1966) have done work in several areas within the Canelo Hills; it is to them that the writer is most indebted for an understanding of the Mesozoic stratigraphy and hence the structural geo­logy of the central Canelo Hills.

Field and Laboratory WorkField work was initiated in December, 1966, and

continued through the summer of 1967. Mapping was done on an enlarged copy of the U.S.G.S. O'Donnell Canyon, 7.5 minute, topographic map at a scale of one inch equals one thousand feet.

An understanding of structural geology within the area was facilitated by walking traverses spaced one thousand

feet apart across the tectonic strike. Attitudes were plotted where possible at 200 foot intervals along these traverses.

Stratigraphic sections were measured with a Jacobs staff graduated at six-inch intervals. A sample was ob­tained from each unit described from which a petrographic thin section was cut. Terminology for the classification of limestones is that of Folk (1962) and is summarized in Appendix I. The terminology of bedding descriptions is also given in Appendix I. The colors of the rocks were determined through use of the Rock-Color Chart (Geol. Soc. America,1963) .

The term, "orthoquartzite," is used for sandstones having more than 90 per cent quartz that are cemented with silica in optical overgrowth. The term, "quartzite," is applied to sandstones with more than 75 per cent, but less than 90 per cent, quartz generally cemented by a mineral other than quartz. "Arkose" is the term applied to sand­stones with more than 25 per cent feldspar grains.

7

CHAPTER 2

GENERAL GEOLOGY

The principal feature of the Canelo Hills is a northwest-trending belt of Paleozoic and younger rocks that extends from Canelo Peak to the northern end of the range. South of Canelo Peak only Mesozoic rocks are exposed.

Structurally the Canelo Hills comprise a fault block tilted to the southwest. Cross-faulting, however, allows for the division of the Hills into three blocks on the basis of the amount of upfaulting: a complexnorthern block consisting of Paleozoic and Mesozoic rocks, a central block composed mainly of Paleozoic limestones, and a southern block of Mesozoic rocks that may be the simplest structurally. This thesis is concerned primarily with the southern part of the central Canelo Hills block.

Regionally it would be expected that the area would show features of horizontal compression since thrust faults have been described by Feth (1947) and Cetinay (1967) in the Canelo Hills; Alexis (1944) and Weber (1950) in the Huachuca Mountains; and others in the Mustang, Empire and Santa Rita Mountains farther to the north. Such is not the case, how­ever, as only minor folding exists; and thrust faults are

8

probably not present in the Canelo Hills. Tectonic structures indicate that the acting stresses have been tensional.

The ages of the rocks in the central Canelo Hills range from Late Cambrian through Quaternary. No Pre- cambrian rocks are exposed. With the exception of the Ordovician and Silurian Periods, the Paleozoic portion of these rocks includes representatives of every period from the Cambrian through Permian. The top part of the Upper Cambrian Abrigo Limestone is the oldest formation exposed. Above it, in ascending order, are the Devonian Martin Formation, Lower Mississippian Escabrosa Limestone, Pennsylvanian Horquilla Limestone, Permo-Pennsylvanian Earp Formation, and the Permian Colina Limestone. Locally, part of the Permian Scherrer Formation is also present.The Paleozoic rocks may be readily correlated with well- established sedimentary sections elsewhere in southeastern Arizona.

Above the Paleozoic rocks are the Canelo Hills Volcanics in fault contact with the Colina Limestone. The Canelo Hills Volcanics are the first definitely established volcanic and sedimentary rocks of Triassic-Jurassic age recognized in southern Arizona (Hayes and others, 1965). This group is in turn overlain by the Cretaceous Bisbee Group and then Tertiary, or younger, consolidated and

9

10unconsolidated deposits. The Bisbee Group is the youngest deformed formation in the central Canelo Hills.

CHAPTER 3

PALEOZOIC STRATIGRAPHY

Paleozoic rocks exposed in the Canelo Hills have been correlated with those in other areas on the basis of similar lithology and faunal content. Widespread marker beds and zones (Abrigo upper quartzite ledge, Horquilla basal residual chert bed, Earp red chert-pebble conglomerate and the upper Horquilla Neospirifer zone) are prominent and generally readily identifiable. These markers and faunal zones not only simplify stratigraphic correlation, but they make structural interpretation possible.

Cambrian System-Abrigo Limestone Ransome (1904, p.3) designated the sequence of

carbonate rocks overlying the Bolsa Quartzite near Bisbee, Arizona, as the Abrigo Limestone with its type locality in Abrigo Canyon. Within the thesis area, the Abrigo Limestone occurs in the low foothills of the northeast corner of the area. From there it extends to the north paralleling the higher hills, but itself forming only gentle slopes. No­where in the central Canelo Hills is a complete section known; instead the Abrigo Limestone is found faulted against younger rocks, generally Mesozoic or Tertiary in age.

11

12Limestones predominate over other rock types in

the Canelo Hills section (Appendix II); and in general they are characteristically laminated or thin bedded and pink in color. At the top of the section, the limestone beds become increasingly sandy and dolomitic and grade into a 3 - 4 foot quartzite ledge. Intrabeds of blue- gray argillaceous limestone give the generally pink Abrigo Limestone a banded appearance.

The measured thickness of the Abrigo Limestone in the central Canelo Hills was determined to be 158 feet in the streambed flowing into Rattlesnake Dam.

No fossils were found in the Abrigo Limestone in the area of the report; however, the lithology is distinc­tive and correlation based on lithologic similarities with other areas is definite.

The environment of deposition of that part of the Abrigo Limestone exposed in the area is thought to be that of a regressing sea. This is reflected by the increase in the proportion of sand and clastic limestone material towards the top of the formation. Fig 2 is an energy level diagram that plots inferred energy of deposition against the stratigraphic sequence. Although oscillations probably occurred, the diagram clearly shows the increasing agitation with time as the Abrigo Sea regressed from thearea.

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15

*1 '2 *3 "l "2 "3 ml "'2 II>3 IV, IV2 IV3 V, V2 V j

stronglyquiet LIMESTONE TYPES agitatedwater waterFig. 2. El Diagram for the Abrigo Limestone. Criteria,used in the construction of this figure are taken from Table 2.

14Pre-Devonian Unconformity

A hiatus spanning the time from Upper Cambrian to Upper Devonian is represented by the pre-Devonian uncon­formity. However, in the Canelo Hills, this hiatus is demonstrated by only a slightly irregular surface on the top of the Abrigo quartzite ledge (Fig. 3). Some structural discordance has been locally noted; however, this is prob­ably more the result of intraformational movements than of pre-Devonian tectonic activity.

Devonian System-Martin Formation Ransome (1904, p. 3) described the Martin Limestone

as exposed on Mount Martin in the Bisbee quadrange. Since that time the Martin Limestone has been widely recognized over southern and central Arizona. In the Canelo Hills, it disconformably overlies the Upper Cambrian Abrigo Lime­stone. The outcrop extends from the northeastern portion of the mapped area towards the northwest, forming a topo­graphic low along the flank of the "secondary hills." Southeastward it passes beneath the alluvium (occasionally cropping out) until it is faulted out of the section. The high percentage of dolomite and sandstone in the Canelo Hills compels the author to refer to this unit as the Martin Formation as it is called in central Arizona.

15

Fig. 3. Slightly irregular contact between Abrigo Limestone on the right and Martin Formation. Both the hammer and the staff lie on the contact.

16The basal part of the Martin Formation consists

of predominantly thin-bedded to laminated sandy dolomites. Upwards in the section, the bedding is thicker and the percentage of sand decreases as the percentage of lime­stone increases. Dolomite makes up 70 per cent of the formation, whereas limestone and sandstone make up about 15 per cent each. The overall colors of the Martin Forma­tion are pastel pink and brown on the weathered surfaces; however, in the upper part of the formation, darker grays are common indicating the increasing proportion of limestone.

The Martin Formation rests on a slightly irregular surface on the Abrigo Limestone and is about 278% feet thick (Appendix II). No irregularity was noted at the con­tact between the Martin Formation and the overlying Esca- brosa Limestone. Instead the contact is arbitrarily placed at the top of the uppermost slope-forming dolomite bed. Generally a raspy leached dolomite is present at or near the contact, but this is not always so. Above the leached zone, a thin-covered interval conceals the actual contact.

The age of the Martin Formation has been established as Late Devonian (Stoyanow, 1936, pp. 486-487) for southern Arizona. In the area mapped, correlation with other areas is possible by lithologic similarities and the faunal assemblage. Fossils collected include Coenites sp. and Zaphrenthis sp.

17The Martin Formation in this area appears to

represent a shallow sea deposit. The El diagram (Fig. 4) shows that the initial deposits were formed in water oscillating between moderately deep and shallow. With time, however, the depth of the Devonian sea became stabilized, and deposition in moderately shallow water took place. The El diagram also indicates that erosion prior to deposition of the Escabrosa Limestone destroyed the final regressive phase of the Martin Formation. Since dolomites are often associated with evaporite deposits, the Martin Formation may reflect a somewhat restricted, saline seaway or near shore facies.

Mississippian System-Escabrosa Limestone The Escabrosa Limestone was named by Ransome

(1904, p. 4) for exposures on Escabrosa Ridge in the Bisbee quadrangle, Arizona, where 700 feet of Mississip­pian strata occur.

Within the area under study, the Escabrosa Lime­stone crops out in a wide band across section 7. This outcrop then continues both northwest and southeast conforming to the regional strike of the homocline. Along this outcrop, the Escabrosa forms both topographic highs and lows (Fig. 5).

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200-

I, l2 13 H| l«2 II3 "U III3 IV, 1V2 IV3 V, v2 V3

quiet stronglywater LIMESTONE TYPES agitated

wa terFig. 4;. El Diagram for the Martin Limestone. Criteria used in the construction of this figure are taken from Table 2.

19

pHi—I I V)•H Cti *HX U 4-»«/) ti 0) •Cd M <u ti uW X! O-H04-1 u w aJh O tZ) CZ)-o "0 0 ) 0id >N <u e EU PH M -HtZ) <D hJ 4-1W J-t rH O•h cd cd

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u V) 3 O •h no a) cr fi cd o od doCZ) (Z) o 0)o O x E a • oE o 4-1 4-1 0 0 3 0 P O O PO P 0) 4-1 CZ) CZ) V) Q) a, »h <u cd i-h

E X)pH .H P• i—i i—1 p cd m «h cd43 Cd 3• CZ) 0) ^ OO CD O 3 O •H j3 O 43tL, t-i 43 N CZ)

20The lithology of the Escabrosa Limestone is uniformly carbonate; only minor amounts of dolomite exist.Essentially the formation is composed of dark and light, coarse-grained, thick-bedded, intraclastic limestones and micrite. Chert occurs as bedded nodules up to 2 feet in diameter in the lower 190 feet of the section, but are most abundant in beds about 60 - 90 feet from the base. Although not noted in the stratigraphic section (Appendix II), at least two lenticular intraformational limestone conglomerates are present. The Escabrosa Limestone is 516*5 feet thick.

The formation is exceedingly fossiliferous; several ledges are reefoid in character. The faunal assemblage of a collection from the central Canelo Hills includes Syringopora sp., Lithostrotionella confluens, Hexagonaria sp., and members of the class Crinoidea.Faunal content, lithological similarities, and stratigraphic position of the Escabrosa Limestone between the dolomites of the Martin Formation and the basal residual chert bed of the overlying Horquilla Limestone serve to correlate and date the formation.

Moderate to shallow water deposition is the inferred origin of the Escabrosa Limestone. The abundant corals found in growth position probably lived in shallow, agi­tated, clear water. Intraclastic limestones and lenticular

21conglomerates also support this conclusion. However, some beds are massive micrite and may be deeper water deposits. These concepts are summarized in Figure 6 which shows that early deposits of the Escabrosa Limestone occurred in agitated water, whereas later deposits occurred in quieter water.

Post-Escabrosa DisconformityThe Escabrosa Limestone has been established as

Early and Middle Mississippian in age; beds of Late Mississippian age have not been recognized in southeastern Arizona. In addition, earliest Pennsylvanian strata are also missing in southern Arizona. This hiatus is repre­sented in the central Canelo Hills by a thick bed of iron- stained chert thought to indicate a residual deposit left by the erosion of Late (?) Mississippian strata (Fig. 5) prior to deposition of the Pennsylvanian Horquilla Limestone.

The topographic expression of this bed is poor; it appears only as a band of red, cherty rubble at the surface. The bedding is obscured, and the cementing agent is unknown. These facts do not permit a true measure­ment of the bed’s thickness or determination of contact relations to either the Horquilla or Escabrosa limestones.

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I3 ll| "2 U3 ml ln2 lu3 ,vi 'V2 iv3 V, v2 v3

quiet strongly •water LIMESTONE TYPHS agitated

waterFig. 6. El Diagram for the Escabrosa Limestone. Criteria used in the construction of this figure are taken from Table 2.

23Pennsylvanian and Permian Systems

Naco GroupThe Naco Limestone was named by Ransome (1904,

pp. 4-5) for limestone overlying the Escabrosa Limestone in the area of Bisbee, Arizona. Later work revealed that fossils from this unit were of both Pennsylvanian and Permian ages. Gilluly, Cooper, and Williams (1954) pro­posed to divide the originally defined Naco Limestone into formations but retain Naco as a group term. Bryant (1955) summarized these changes and proposed that the Pennsylvanian Horquilla Limestone, Permo-Pennsylvanian Earp Formation, and all the Permian Formations in southern Arizona be designated as the Naco Group.

In the area mapped, the Pennsylvanian System is represented by the Horquilla Limestone and the lower portion of the Earp Formation. The Permian System is represented by the upper part of the Earp Formation (previously described), the Colina Limestone, and numerous gravity slide blocks derived from the Scherrer Formation or the Concha Limestone. The blocks from the Concha Limestone are all too small for meaningful study.

Horquilla Limestone. The Horquilla Limestone was named by Gilluly, Cooper, and Williams for Pennsylvanian strata exposed on Horquilla Ridge, Cochise County, Arizona.

24In the Canelo Hills, the Horquilla Limestone is

exposed along the east side of the "secondary hills."The contact between the Horquilla Limestone and the under­lying Escabrosa Limestone is a disconformity; the contact between the Horquilla Limestone and the Earp Formation is a fault.

As a consequence of faulting and the inherent weak­ness of the rock type, the Horquilla Limestone generally forms a subdued topography of steps and ledges superimposed on a gentle slope.

The Horquilla Limestone was not measured in the mapped area; however, Cetinay (1967) measured a faulted section of the lower part of the Horquilla Limestone in section 1 about lh miles north. In that section, Cetinay describes 170 feet of medium-bedded, silty limestones interbedded with thin, limy shales. In general, the limestone beds are gray as opposed to the pink or red shales or silty limestones.

Within the area under study, a thicker section of the Horquilla Limestone is known to exist than that measured by Cetinay. Poor exposures, especially of the shaley beds, do not permit measurement; but it is estimated that 650 feet of lower Horquilla Limestone is present. Baker (1962, p. 45) measured an incomplete section of the Hor­quilla Limestone in the Patagonia Mountains and arrived at

25thickness of 1,119 feet. Evidently the Burro fault has cut out 500 to 600 feet of the section in the Canelo Hills.

The Horquilla Limestone is abundantly fossiliferous and is generally readily recognizable on this basis (Fig.7). The contact with the overlying Earp Formation was defined as that point where elastics become predominant over the limestone and is thus arbitrary and gradational.In the central Canelo Hills, the contact is easily identi­fiable because clastic beds of the Earp Formation are faulted against definite Horquilla Limestone beds. The upper Horquilla elastics were evidently cut out by the faulting. The faunal assemblage for the Horquilla and other formations of the Naco Group are given in Appendix III.

The Horquilla Limestone is thought to represent the initial deposits of a sea that covered southern Arizona for much of the Pennsylvanian and Permian periods. Trans­gression must have been rapid as no reworking of the chert zone at the base of the Horquilla is evident. The begin­ning of Permo-Pennsylvanian regression is at the top of the Horquilla Limestone, where limestones containing terri­genous material are present.

Earp Formation. Gilluly, Cooper, and Williams (1954) defined the Earp Formation from exposures on Earp Hill near Tombstone, Arizona.

26

Fig. 7. Horquilla Limestone containing Chaetetes favosus, field guide to Hor- quilla Limestone.

27Rea (1967) subdivides the Earp Formation into three

members on the basis of lithology. Rea calls these the lower limy member, the middle terrigenous member (containing most of the clastic beds within the formation), and the upper interbedded clastic and carbonate member. In addi­tion, Rea discusses the stratigraphy of a red chert- pebble conglomerate within the middle terrigenous member that he believes is probably an isochronous unit across southeastern Arizona and southwestern New Mexico.

The thickness of the Earp Formation cannot be deter­mined in the central Canelo Hills due to structural complex­ities. However, a partial reconnaissance section was measured and is generally described in Appendix II.

In the Canelo Hills, part of the upper interbedded member and part of the middle terrigenous member can be recognized; however, they are not mappable as separate units. The red chert-pebble conglomerate (described in Appendix II) is present and forms an indispensible marker for interpreting structure in the Earp Formation (Fig. 8).A second conglomerate 8 feet thick lies 10 feet beneath the chert-pebble conglomerate. This second conglomerate is composed of subrounded limestone pebbles as much as 3/4 inch in diameter. This sequence is useful in determining tops of beds when structural overturning is suspected.

28

Fig. 8. Faulted outcrop of the chert- pebble conglomerate of the Earp Formation. Pick lies along slickenside surface of conglomerate.

29Unfortunately the shaley zone just beneath the chert- pebble conglomerate is the locus for many strike faults, and the lower conglomerate is often cut out. In the section measured in the Canelo Hills, a thickness of 574 feet is present. No faulting is known in this interval, but that does not preclude its existence.

The age of the Earp Formation has been discussed extensively by others (Rea, 1967; Dublin, 1964; Gilluly, 1956; and Bryant, 1955) and will not be further pursued here. The Pennsylvanian-Permian boundary lies within the Earp Formation. Correlation of the stratigraphic section is made possible by its fossil content (Appendix III) and the chert-pebble conglomerate. The contact with the under­lying Horquilla is a fault that brings Chaetetes favosus (field guide to the Horquilla Limestone) in contact with the chert-pebble conglomerate. The upper contact of the Earp Formation is a conformable gradation with the Colina Limestone.

Conditions of deposition for the Earp Formation are difficult to infer in an area where the stratigraphy is so disturbed. However, the middle terrigenous member with its conglomerates, cross-laminated silts, and sand­stones (Fig. 9) probably represents the culmination of regression that had begun during the deposition of the Horquilla Limestone. Rea (1967, p. 37) believes that the

30

Fig. 9. Block of ripple-marked, orange­weathering dolomite of the Earp Formation. Outcrop occurs twice on south side of Burro Hill, due to faulting by the Tri-Peak fault.

31high point of the regression was reached during the deposition of the chert-pebble conglomerate which he interprets to be of terrestial origin. Under his hypo­thesis, the conglomerate would have been deposited on flood plains or tidal flats by meandering streams.

Deposition of the upper part of the Earp Formation took place during renewed transgression and is represented by a typical transgressive sequence of clastic material overlain by massive Colina Limestones.

Colina Limestone. Gilluly, Cooper, and Williams (1954) named the Colina Limestone for exposures on the west side of Colina Ridge near Courtland, Arizona.

The Colina Limestone conformably overlies the Earp Formation in the central Canelo Hills. It crops out in the southern part of the area where it forms a long, high ridge. An estimated 200 feet of Colina Limestone are present. The upper part of the formation is missing since it is in fault contact with the overlying Canelo Hills Volcanics.

Characteristically, the Colina Limestone is a massive-bedded, black limestone. Locally, these beds weather light gray or buff with an elephant hide-like texture. Few clastic beds are in the section, but locally a light silty dolomite does crop out. Samples of the black limestone were dissolved in dilute hydrochloric acid and

32yielded about five per cent insoluble clayey residue. Thin sections of these same samples show them to be mostly micrite.

The large gastropod Omphalotrochus is an important guide to recognizing the presence of the Colina Limestone. They are exceedingly abundant on the ridge near the center of section 13 where several individuals may be found per square foot of surface area.

Much chert in the form of irregularly shaped nodules or "bulbs" appears in that part of the Colina Limestone exposed in the central Canelo Hills. These chert nodules are generally black or gray and range from a few inches to one or two feet in diameter. Small quartz geodes are associated with these nodules.

The Colina Limestone is Early Permian in age. The characteristic black color, the Omphalotrochus fauna, and its distinctive stratigraphic position overlying dolomites of the Earp Formation make the Colina Limestone readily identifiable.

The Colina Limestone marks the maximum transgression into southern Arizona by a Permian sea. The massive bed­ding, constant lithology, and lack of terrigenous sediment imply that sources were far removed. Fossils present (Appendix III), however, suggest relatively shallow waters.

33During Lower Permian time, the Canelo Hills area must have been a small portion of a broad shelf with little nearby relief.

Scherrer Formation. The sandstone unit overlying the Colina Limestone or locally the Epitaph Dolomite, was named the Scherrer Formation by Gilluly, Cooper, and Williams (1954, p. 27) for its exposures in the northern Gunnison Hills. At the type area, the formation consists of two thick sandstone units separated by a thick dolomite. Luepke (1967) discusses the stratigraphy of the Scherrer at various localities in southeastern Arizona.

In the central Canelo Hills, occurrences of the Scherrer Formation are limited to the numerous "exotic" blocks in the southern part of the mapped area. These occurrences are apparently gravity slide blocks, and their origin will be discussed in later portions of this paper.

A block of Scherrer sandstone caps the ridge north of New Tank. This block overlies Colina Limestone, a portion of which is also included within it. One of the present problems in the Permian stratigraphy of southern Arizona is the local occurrence of the Epitaph Dolomite between the Scherrer Formation and Colina Limestone. The Canelo Hills is an area in which the Epitaph Dolomite is absent. Bryant (personal communication) has suggested that the Epitaph Dolomite is not a distinct formation but merely a local dolomite facies of the Colina Limestone.

34Luepke (1967, pp. 36-41) discusses several possi­

ble origins for the Scherrer Formation. For the lower, cross-bedded member, she suggests the possibility of aeolian deposition, but seems to favor the reworking of dune or beach deposits by a shallow sea. The Scherrer sandstone in the central Canelo Hills appears to be a water-laid deposit of beach or dune sand. The individual grains are rounded and well sorted; and the rock is practi­cally monomineralic. Cross-bedding is apparently the best criteria for inferring depositional environment. The cross­bedding in the central Canelo Hills is in thin sets (Fig.10) with high angle contacts. Although the implied current direction (N 74°E) is negated by subsequent gravity sliding, the associated consistancy factor for 30 measurements should still be valid. The value of the consistancy factor is 0.506, a value too low for rocks generally considered to be wind deposits.

The age of the Scherrer Formation as exposed in the New Tank gravity block is established by the fossilif- erous Colina Limestone that lies immediately beneath the sandstone. A fossil collection from this block (Appendix III) has been described as typically Colina Limestone (A1 Reid, personal communication). The distinctive cross- bedded orthoquartzite overlying the Colina Limestone is easily correlated with other sections of the Scherrer Formation on the basis of lithology.

35

Fig. 10. Cross-bedding in Scherrer sandstone; gravity slide block.

Concha Limestone. The Concha Limestone is only present in the central Canelo Hills as exotic blocks interbedded in the Canelo Hills Volcanics. The small size of these blocks makes detailed study meaningless.

CHAPTER 4

MESOZOIC AND CENOZOIC STRATIGRAPHY

Mesozoic RocksSedimentary rocks of Cretaceous age have long been

recognized throughout southern Arizona; but until recently no sediments could be definitely ascribed to the Triassic or Jurassic Systems. Instead it was believed that southern Arizona was a highland that supplied sediment into adjacent areas during Early and Middle Mesozoic times.

However, in several areas, recent workers have described rocks that they believed were Early Mesozoic; but due to structural uncertainties, they were unable to prove the age. The Canelo Hills provide the first occur­rence of Triassic-Jurassic sediments that can be dated with certainty. Because of the importance of the these rocks in understanding the geology of the Canelo Hills and the potential regional implications involved, it was desirable to study them in detail. The stratigraphic section des­cribed in the appendix is the first available for the lower member of the Canelo Hills Volcanics.

37

38Triassic and Jurassic Systems

Canelo Hills VolcanicsName and Distribution. The Canelo Hills Volcanics

were named for exposures of interbedded volcanic and sedi­mentary rocks found in the Canelo Hills, the type area, by Hayes, Simons, and Raup (1965) .

This group of rocks, although not present in a complete continuous sequence anywhere, comprises the main ridge of the Canelo Hills. The ridge itself is a strike ridge; and the southwestern slope is a dip slope. The regional dip on the Canelo Hills Volcanics is less than that of the Paleozoic rocks and averages only 23°SW. Structurally the Volcanics are in fault contact with the Colina Limestone. Elsewhere these rocks crop out in the streambed at Rattlesnake Dam and to the north in sections 5 and 6. At these localities, they are probably in fault contact with Paleozoic strata on the west and the Bisbee Group on the east.

Lithology. The Canelo Hills Volcanics may be subdivided into three major units: (1) a basal interbeddedsequence of coarse limestone conglomerate, arkosic sand­stone, and volcanic flows; (2) an intermediate unit composed of rhyolite lava flows with a few interbedded red, welded tuff units; and (3) a thick sequence of welded tuff. Only the lower two subdivisions are present within the area mapped. Near the Canelo-Lochiel road, the Western Canyon

39fault has apparently downdropped the Lower Mesozoic sec­tion; and the intermediate unit of rhyolite flows is exposed. West of this area near Double Tank, the basal interbedded unit is exposed. The measured stratigraphic section (Appendix II) shows that the basal unit is capped by several hundred feet of rhyolite showing a weakly developed welded tuff texture. This rhyolite represents the lower beds of the intermediate member. The upper welded tuff member is present east of the Canelo-Lochiel road.

An outstanding characteristic of the basal unit is the presence of brecciated blocks of Upper Paleozoic limestone enclosed by limestone and volcanic conglomerate or volcanic flows. These blocks range from a few feet to several thousand feet (?) in length (Plate 1, Fig 11).They are predominantly composed of rocks derived from the Colina Limestone, Scherrer Formation, or Concha Limestone. Bedding in the blocks is only weakly evident, but does parallel bedding in the enclosing Canelo Hills Volcanics.

These "exotic" blocks, as they will be referred to hereafter, are contained only in the basal or inter­mediate members of the Canelo Hills Volcanics. So far none are known to exist in the upper welded tuff member, although one block was found just beneath the rhyolite- welded tuff contact east of the Canelo-Lochiel road. Apparently these exotic blocks may be found at any strati­graphic level in the basal and intermediate members.

s S *-c ■ —k----------------------- — — - r-

II

B w B iT_ #$

jg- :gF• .*■'*

3 u ^ T . V.

$ 8 . m

Fig. 11. Photo mosaic showing the Manzanita Block of Paleozoic limestone interbedded in the Canelo Hills Volcanics. This block is approximately 3,000 feet in length, but less than 100 feet thick along the outcrop. It lies in the upper part of the basal member of the Canelo Hills Volcanics.

o

41For example, a block is in contact with the dike sepa­rating the Paleozoic section from the Canelo Hills Volcanics; the Manzanita Block is in the upper part of the same basal interbedded member (Fig. 11). The block along Lochiel Road is contained within the intermediate rhyolites (Fig. 12); and the block near Middle Canyon is near the top of the intermediate rhyolite member (Plate 1).

Thickness. The composite thickness for the three members of the Canelo Hills Volcanics has been estimated by Hayes, Simons, and Raup (1965) to be a minimum of 9,400 feet. Within the thesis area, the lower 2,179 feet were measured and described (Appendix II).

Age and Correlation. The Canelo Hills Volcanics are the first sedimentary and volcanic rocks found in southern Arizona that can be dated with certainty as younger than Early Permian and older than Early Creta­ceous (Hayes, Simons, and Raup, 1965). The inclusion of exotic blocks within the lower and intermediate members proves the members to be younger than the Paleozoic blocks they contain. Hayes, Simons, and Raup (1965, p. 4) describe the upper contact of the welded tuff member with an over- lying conglomerate that they correlate with the Bisbee Group (Early Cretaceous). They conclude that the welded tuff member is pre-Cretaceous and assign the Canelo Hills Volcanics to the Triassic-Jurassic Systems. Their con­clusion is substantiated by a potassium-argon isotope age

42

Fig. 12. Lochiel Road block. Paleozoic limestone encased by rhyolites of the Canelo Hills Volcanics. Volcanics in foreground; limestone just in front of treeline.

43determination of biotite from the welded tuff of 173±7 million years. This places the welded tuff in the Late Triassic or Early Jurassic.

The only other volcanic rocks of this age reported in southeastern Arizona crop out in the Gunnison, Johnny Lyon and Red Bird Hills 50 miles to the northeast. These occurrences have been described by Cooper (1959,1960), and Cooper and Silver (1964) , and are known as the Walnut Gap Volcanics.

Dr. R. Wilson of the University of Arizona, Depart­ment of Geology, has shown the writer a sequence of thickly cross-bedded sandstones in the Gardner Canyon area of the Santa Rita Mountains that bears a strong resemblance to the sandstones in the basal interbedded member of the Canelo Hills Volcanics. At the northern end of the Canelo Hills, the conglomerate is thinner, sandier, and less coarse than it is in the central Canelo Hills. Intrabeds of limestone are also present in the northern Canelo Hills. Cross-bedding in the north is on a smaller scale than in Gardner Canyon. A correlation between these three areas is possible, but would require additional work. Drewes (1966), however, believes the sandstones in Gardner Canyon are Lower Triassic in age. Other tenative correlations are discussed in the following section.

Environment of Deposition. No fossils have been found in the Canelo Hills Volcanics; however, small scale

44cross-bedding and good sorting in some beds of the basal member imply deposition by water. The angularity and size of fragments in the conglomerates suggest rapid deposition, short transportation, and no reworking of material derived from a nearby source. The presence of exotic blocks, probably resulting from gravity slides or landslides, indi­cates that (1) the adjacent paleotopography was steep or (2) periodic uplifts of nearby areas occurred. Structural movement during this period of time must have taken place to allow for subsidence of the basin that accumulated the sediments.

The geometry of the basin can be inferred from deposits in the thesis area and those reported by Feth (northern Canelo Hills, 1947) , Baker (Patagonia Mountains, 1962), Alexis (north Huachuca Mountains, 1949), Weber (central Huachuca Mountains, 1950), Hayes and others (southern Canelo Hills, 1965), and Simons and others (Canelo Hills, 1966). A proposed correlation for these areas is presented by Fig. 13 and is discussed in reference to basin geometry in the following sections.

The Patagonia Mountains and the central Canelo Hills stratigraphic sections are remarkably similar in the lower part, thus implying that they occupied a similar position on the Canelo Hills Basin paleoslope. East of the Canelo Hills, however, limestone conglomerates predomi nate. This suggests a source of limestone debris to the

Fig. 13.

Proposed Correlation of the Canelo Hills Volcanics.

Corrcl Ccnyonvm. Oucuosna volconicsP o to g o n io h/ountoins ( B a k e r ,1962)

i m m m m

Ccnclo Rbi North Conolo Hills (Feth, IS 4 7 )

East-Central Conelo Hills (This report)Concio Kills Voiconicc.

(Kayes and others , 1965)

o ° „ ° ' Huochueo Mountains1st. con l. frn. clastic fm. (Ai .s,1949, Weber, IS50)

O oa-l-j Lj 11 n

<— , M n$ro '» :<

SH i. .z cC

t- 1 15<6

>:\;o33

w? 3C -

Uwzr

Xc.Ci I f

c K

o3

§c* i/ a *r.>

u

St7

46east. The rhyolite tuffs at the top of the basal member of the Canelo Hills Volcanics appear to have originated from a point south or west of the central Canelo Hills since they are not present in the Huachuca Mountains or northern Canelo Hills. In the area mapped, they interfinger with the conglomerates indicating a possible secondary source area during the time limestone debris poured in from the east. These conclusions are supported by the finer-grained deposits, including thin limestones, in the northern Canelo Hills. The Triassic-Jurassic basin opened and deepened towards the northwest and may have been elongate in that direction.

The exotic blocks are believed to be gravity slides or landslides into the basin; however, their source is unknown. As they appear to be larger in the southern Canelo Hills than they are in the northern Canelo Hills, they may have entered the basin from the south or southeast and slid along a muddy bottom towards the northwest.

It is more likely that an escarpment existed parallel to the basin, along which periodic landslides took place towards the west. The large size of the blocks could be a result of the height of the escarpment or the nearness of the escarpment to the final resting place of the blocks. The blocks would be expected to break up if they were transported very far.

47The blocks have remained together as a unit of

deranged bedding slabs even though thoroughly brecciated during initial movement. Landslides could account for this fact. Thin veinlets and stringers of red arkosic sandstone cement the limestone breccia fragments. These veinlets probably squeezed up into the limestone blocks following landsliding. Additional deposition of sand­stone and conglomerate eventually buried the exotic blocks.

Other exotic blocks are enclosed in rhyolite flows. These were probably landslides that were resting on a flat terrain when overrun by the volcanic flows.Simons and others (1966) believe that these blocks may have been plucked up and rafted by the lava flows.

The intermediate and upper members of the Canelo Hills Volcanics were not studied in detail, but a tenative correlation of them is presented in Fig. 13.

Cretaceous System-Bisbee GroupThe Bisbee Group is not present within the immediate

area mapped. However, north of the area, a conglomerate- sands tone -shale sequence is present which is assigned to the lower part of the Bisbee Group. The Bisbee Group in this area is probably in fault contact with the basal Canelo Hills Volcanics. The contact was not mapped but can be readily distinguished on the basis of differing

48lithologies. The Bisbee Group conglomerate is predomi­nantly gray and contains only small amounts of limestone fragments. Typically the fragments consist of a high percentage of coarse-grained intrusive rocks with smaller amounts of volcanic and limestone pebbles. In comparison to this, the basal Canelo Hills Volcanics contain a high proportion of limestone and volcanic fragments and are red in color. The sandstone in the Bisbee Group is coarse-grained, poorly sorted arkose. The color of this rock and the interbedded shales is usually light gray to white.

Elsewhere the Bisbee Group occurs near the town of Canelo and at Lone Mountain. Hayes, Simons, and Raup (1965) report that the Bisbee Group overlies the upper welded tuff member of the Canelo Hills Volcanics at Lone Mountain.

Where observed, the Bisbee Group has been involved in tilting. North of the area mapped, these rocks dip to the northeast. Near Canelo they dip to the southwest; the structure between these outcrops is unknown because of alluvial cover.

Cenozoic Sedimentary and Volcanic RocksGravel deposits, conglomerates, and lakebeds over-

lie older rocks in the lower portions of the thesis area and the nearby vicinity. Generally the sediments are coarse

49unconsolidated debris of the older rocks. These are unde­formed but dip slightly down the gradient of present-day streams. Fresh water (?) lake beds are present at the Canelo Hills Ranch. Except for stream deposits, Cenozoic sediments have not been differentiated on Plate 1.

Cretaceous-Tertiary Dike The Smoke Mountain fault has been intruded by a

rhyolite dike in section 13. This dike consists of finely crystalline rhyolite showing well-developed vertical flow banding (Fig. 14.). The intrusion probably occurred after northeast faulting as it appears that the Double Tank fault has been displaced along the dike. Intrusion was probably forceful.

50

Fig. 14. Vertical flow banding in Smoke Mountain dike. Photo covers an area four feet wide.

CHAPTER 5

STRUCTURAL GEOLOGY

The geologic map of the Canelo Hills published by Hayes and others (1965) shows that the Hills comprise a fault block that has been tilted to the southwest. The breaking of this block by cross-faulting allows for its division into three small fault blocks. These are distin­guished by differing amounts of uplift. This paper is primarily concerned with the southern part of the central Canelo Hills block. Data collected in this area supports the hypothesis that tension has been responsible for struc­tural features present in the central Canelo Hills.

Predominant geologic structures in the area are strike faults (defined as those faults which parallel the strike of the bedding) that show dip-slip movement. These faults are localized within the Earp Formation because of its mechanical anisotropy. Other fault systems are present but are less important. The only significant folding is drag folding along the strike faults.

FoldsIn the central Canelo Hills, all folding, with

one possible exception, is interpreted to be related to51

52

faulting. The related faults are strike faults on which normal dip-slip movements have taken place.

The small folds present in the central Canelo Hills were interpreted to have been caused by drag along faults for the following reasons: (1) drag folding can be observedin vertical cross-section adjacent to Corral fault (Fig. 15) and Dam fault (1/4 mile north of the area mapped); (2) al­though the central Canelo Hills is an area of remarkably uniform dip towards the southwest, strata of the inter­mediate terrigenous member of the Earp Formation generally is repeated along the folds; (3) to account for the regional dip, overturned folds would have to be present; however the sequence of the two conglomerates (page 27) is not known to be reversed at any locality; (4) the lower half of the Earp Formation is not exposed in the central Canelo Hills, a fact inconsistent with the concept of folding; and (5) other formations besides the Earp Formation and the Horquilla Limestone are not cut by strike faults and do not show even minor folding.

Drag folds are confined to the Earp Formation with one exception: the small anticline mapped by Cetinay (1967)in section 6. This drag fold, localized within the Abrigo Limestone, passes through the center of section 6 into the NE$i of section 7. It was formed by normal drag during movement on Dam fault.

Fig. 15. Corral fault. Downdrops Earp strata on the right relative to strata on the left.

54All drag folds and monoclines are superimposed on

a homocline that dips 30° to 40° to the southwest. The fold axes of the flexures generally plunge 20° to 30° to the northwest. The faults eventually die out in the north­west, but the drag folds continue further northwestward as monoclines.

Because they are persistent along strike, drag folds have been useful in tracing faults. For instance, Tri-Peak fault may be followed from section 18, two and one-half miles northwest where Cetinay mapped it as a syncline.

Some faults are located in synclines formed by normal drag on the upthrown side and reverse drag on the downthrown side. Reverse drag is expressed in the field as small tight anticlines, sometimes overturned, adjacent to normal faults. Tri-Peak and Corral faults show such structures large enough to appear in Plate 2.

Theories concerning the origin of reverse drag have been reviewed by Hamblin (1965). Hamblin concludes that normal movement on a curved fault plane tends to pull the fault blocks apart as well as displace them vertically. Adjustments to fill the incipient gap by sagging then develop reverse drag.

One set of folds probably unrelated to faulting is present in the area. This set is in the prominent chert- pebble conglomerate marker bed of the Earp Formation in the NN?$ of section 18. No fault could be found related to this structure. The fold consists of an anticline flanked

55on either side by a shallow syncline. The amplitude of the fold is less than 100 feet. The fold complex plunges gently to the northwest. Small faults cut the marker bed and offset it 20 to 30 feet in a left-lateral sense (Fig 8). The relationship of the fold axis with the trend of these faults suggests that they may have ori­ginated as cross joints during first tilting of the central Canelo Hills block. Neither the faults nor the fold can be traced along their trends.

The anticline mapped by Cetinay (1967) passes north through the center of section 6 and is probably a drag fold. Faulting is revealed by the sliver of Martin Limestone surrounded by Abrigo Limestone just east of his anticlinal axis in the streambed north of Escabrosa Hill. This is probably the same fault mapped in section 7 that downdrops Abrigo Limestone on the east. Cetinay mapped a portion of this fault in section 6, where he shows Martin Limestone on the east downdropped against Abrigo Limestone on the west.

Early FaultingThe parallel relationship of the strike faults to

the strike of the bedding suggests that the faults may be genetically related to tilting of the Canelo Hills block. These faults probably formed as tensional breaks during tilting of the central Canelo Hills block. Somewhat later.

movements allowing for adjustment within the block resulted in additional faulting.

Recognition of the strike faults is not easily done in the Paleozoic limestones exposed in the area mapped. It was for this purpose that nine traverses were completed, spaced at 1,000 foot intervals across the tectonic strike. From the data thus compiled, geologic cross-sections were prepared (Plate 2). Criteria used for recognizing these faults included the omission or repetition of strata, and drag folding. Mechanical weakness within the Earp Forma­tion is suggested by the fact that this unit served as the locus for yielding during tilting of the Canelo Hills block. The appearance of the chert-pebble conglomerate of the Earp Formation adjacent to the faults indicates that the middle terrigenous member of the Earp is the zone in which faulting occurs.

Dam FaultThe Dam fault strikes N25°W as it passes from

Rattlesnake Dam northwest to the well at the center of sec­tion 6. At Porcupine Ridge, the fault is lost beneath Tertiary-Quaternary gravels; however, it may be continuous with other faults further south.

56

57Elsewhere the Dam fault moves upper Abrigo Limestone

into contact with Tertiary-Quaternary conglomerates omit­ting the 500 to 600 feet of lower Abrigo Limestone that are known to exist in nearby areas. Burial of the Abrigo Limestone on the north side of Dam fault makes it impossible to estimate the amount and type of displacement on this fault.

Faults in the Earp FormationFour major strike faults cut the Earp Formation.

These are referred to as the Tri-Peak fault, Corral fault. Valley fault, and Chaparral fault. In addition, at least two others are strongly suggested but could not be abso­lutely proved.

The Earp faults trend N 45°W to N 60°W. The southwest side of all of these faults is upthrown thus causing repetition of strata. Determination of the actual dip of the faults is difficult since vertical sections are rare, and the subdued topography does not express the dip of steep faults. The Corral fault, however, can be observed to dip 65°NE along part of its length. The topographic expression of the Tri-Peak and the Valley faults suggests that they dip more steeply to the northeast.

Chaparral fault is even less well exposed as associated drag folding is poorly developed. This fault.

58like the others, is established by the recurring Earp strata, in particular, the chert-pebble conglomerate.The trace of the Chaparral fault is approximately located, and its dip is assumed to vary between vertical and steeply northeast.

In the absence of planar structures of pre­block faulting age that trend oblique to bedding, the strike-slip component of movement on these faults cannot be determined. However, due to occurrences of the Earp chert-pebble conglomerate, the dip slip can be estimated.By graphical means, a dip-slip component of displacement for the Corral fault was determined to be 580 feet in the vicinity of Hill 5866.

Assuming the Chaparral fault to be vertical, then it must have a dip-slip component of 500 feet. Dip-slip movement of the Tri-Peak fault appears to be on the order of 1,300 feet. However, as inferred on Plates 1 and 2, there may be another fault lying between the lower contact of the Earp Formation and the Tri-Peak fault. This could account for part of the displacement.

Other strike faults in the Earp Formation probably have a similar displacement. Locally, however, the combined effects of strike faults and cross faults has caused greater displacements, as exemplified by the rectangular-shaped occurrences of Horquilla Limestones near Far Tank in section 12.

Slickensides on some fault planes such as the Valley fault indicate that all movements on the Earp faults were not in a vertical sense, but that later movements had a strike-slip component. Drag folding on the Tri-Peak and the Corral faults also illustrates this point. Along the southeastern part of these faults, the strata have been rotated into the faults. This sug­gests that the northern blocks were dragged towards the southeast as well as downdropped relative to the southern blocks.

Burro FaultThe Burro fault strikes N 40°W and dips 30° to 40°

SW. It extends from the southeast corner of section 7 to and beyond the northwest corner of section 1. The northern extension of the Burro fault was mapped by Cetinay (1967) as one fault that bifurcates into a fault on either side of the Horquilla Limestone in section 1. Thus he believes that the Horquilla Limestone is in fault contact with both the overlying Earp Formation and the underlying Escabrosa Limestone. The writer is not in complete agree­ment with this as he has seen the residual red chert bed at the base of the Horquilla Limestone near the top of Third Peak in section 1. Therefore he chooses to believe that a depositional contact exists between the Escabrosa

59

60and Horquilla Limestone, while the contact between the Horquilla Limestone and Earp Formation is a fault.

The dip of the Burro fault is 30° to 40° south­west and is revealed by the topographic expression of the fault at the place where it crosses the saddle on the southern side of Third Peak.

Displacement on this fault is such that the Earp Formation is downdropped against the lower part of the Horquilla Limestone. This displacement is substantiated by the presence of chert-pebble conglomerate of the Earp Formation in near contact with Horquilla Limestone con­taining Chaetetes favorsus.

Taking a thickness of 650 feet for the Earp Forma­tion (average of Baker, Wanless, and Gilluly) and 1,200 feet for the Horquilla Limestone (average of Baker, Wanless, and Gilluly), the Burro fault is estimated to have 1,400 feet of stratigraphic separation, assuming that the Earp conglomerate lies 350 feet from the top of the Earp Formation (Bryant, 1955).

The Burro fault is similar to the strike faults previously described, as it also parallels tectonic strike. This relation makes it almost certainly another member of the same fault system. The low dip on this fault may seem anomalous, but it is probably the result

61of the fault following bedding planes. It is significant to note that this fault is also located in the middle terrigenous member of the Earp Formation just beneath the chert-pebble conglomerate.

Smoke Mountain FaultWithin the area mapped, the Smoke Mountain fault

is established on the basis of a straight contact between lower Mesozoic rocks and the Colina Limestone. Elsewhere in southeastern Arizona, this contact is a highly irregular unconformity.

The Smoke Mountain fault is one of the longest and most significant faults in the Canelo Hills. From the western side of the area, it has been mapped northwestward about four miles to a point where it is lost in the Canelo Hills Volcanics (Hayes and others, 1965). In the mapped area, the fault disappears where the rhyolite dike intruded along part of the fault in section 18 at the point where the lower member of the Canelo Hills Volcanics is present. It may be that the Smoke Mountain fault is offset by faults of the somewhat younger northeast-striking system. The Smoke Mountain fault probably continues to the southeast along the Far Tank jeep trail across the Lochiel Road to point 5291 at which Hayes (and others, 1965, p. 2) mapped the beginning of another fault. This southward extension strikes S 55°E and may be followed for 5 to 6 miles.

62The Smoke Mountain fault is a nearly vertical to

southwest dipping fault. Throughout its length, it closely follows the strike of bedding. Apparent movement on this fault indicates that it may be a rotational fault. In the mapped area and northward, the southwest block has been downdropped. Along the presumed extension to the southeast, the northeast block is downdropped. The hinge line may be along Western Canyon.

The southward extension which is outside the mapped area, was not studied. However, the dip-slip displacement has been estimated within the mapped area for the Smoke Mountain fault. Baker (1963, pp. 49-51) estimates the thickness of the total Concha, Scherrer and Colina Formations to be 1,375 feet in the Patagonia Mountains ten miles to the southwest. Within the mapped area, only 200 feet of the Colina Limestone are present. This implies that possibly 1,175 feet of upper Permain rocks have been cut out. Erosion prior to faulting may be responsible for part of this decreased thickness.

East to West Striking FaultsAn east-striking system of faults is poorly devel­

oped over the mapped area. Of those present, only two appear to be of significance. One of these partially bisects section 13 into north and south halves. Neither the direction of dip nor the amount of displacement on this

63fault could be established as relative movement of the north and south blocks is not clear due to later faulting by northeast-striking faults. However, the fact that the Smoke Mountain fault shows no displacement on the pro­jected trend of this fault implies that this east-striking fault is a splay of Smoke Mountain fault.

The other east-striking fault of importance extends east from the Burro Tank area for a distance of less than one mile. Along this fault, the northern block has been downdropped relative to the southern block. No strike-slip movement is indicated by attitudes taken in the limestones. Apparent left-lateral movement of the residual chert bed at the bottom of the Horquilla Limestone allows for the calculation of a stratigraphic separation of approximately 400 feet. No displacement of Burro fault by this fault could be mapped. This east-striking fault is probably a splay of the Burro fault.

Late Northeast Striking FaultsNortheast-striking faults are numerous, but gener­

ally are of small magnitude, in the central Canelo Hills. Locally, however, the combined effect of the strike faults with these northeast cross faults has resulted in small horst structures in section 12. Unfortunately these horsts are in a relatively level valley, thus the bounding

64faults are difficult to follow except where the resistant Horquilla Limestone forms low scarps surrounded by rocks of the incompetent Earp Formation.

The attitude of the northeast cross faults is variable; however, most strike about N 60°E, with an average dip of 66° to the southeast.

Burro Tank fault is an east-striking fault for which the displacement can be estimated. The chert-pebble conglomerate of the Earp Formation is offset along this fault. Displacement is left-lateral, over a distance of about 500 feet. Dip slip is estimated at 300 feet. The line of outcrops of the conglomerate along the Burro Tank fault may be the result of strike-slip movement or several left-lateral displacements in a fault zone.

Western Canyon Fault. The Western Canyon fault is a cross-fault that is mapped partly on the basis of changes in alluvium and partly by exposures in section 24. Close to the Lochiel Road, alluvium is predominantly volcanic. This changes sharply to a greater abundance of limestone rubble along the fault shown on Plate 1. Believing that the alluvium reflects the underlying rock type, the Western Canyon fault was inferred. This seems logical since the hills on the east side of the Lochiel Road consist mainly of the welded tuff member of the Canelo Hills Volcanics.

The best exposures of the Western Canyon fault are in section 24. The contact relationship is never sharp, but the southward extension of the Western Canyon fault is evident where the basal member of the Canelo Hills Volcanics has been positioned against the inter­mediate rhyolite member of the same formation. The Western Canyon fault is the boundary fault on the southern end of the central Canelo Hills fault block.

Displacement of strata by the Western Canyon fault cannot be accurately determined since the area is also affected by the Smoke Mountain fault and the fault passing through Double Tank. However, east of the Western Canyon fault, the upper beds of the basal Canelo Hills Volcanics must be offset towards the north at least one mile. This would require a vertical displacement of at least 2,600 feet. The amount of strike-slip movement is unknown.

Exotic BlocksLarge blocks of upper Palezoic limestone enclosed

or underlain by the lower or middle member of the Canelo Hills Volcanics (Figs. 11 and 12) are common in the area of Canelo Pass. Similar occurrences in other Mesozoic rocks have been described elsewhere in the Canelo Hills, Santa Rita Mountains and Patagonia Mountains (Simons and others, 1966). Plate 1 shows the distribution and size of some of these blocks. Others may exist further

65

66northwest of Canelo Pass where only reconnaissance work was done. The blocks range in size from a few feet to several thousand feet long and are as much as 100 feet in outcrop thickness. Those studied consist of bedding slabs derived from the Concha Limestone, Scherrer Formation, or the Colina Limestone.

Generally the blocks are brecciated and the bedding destroyed, especially in the smaller blocks. In some of the larger blocks, bedding is poorly preserved as are silicified fossils suitable for dating the rocks comprising the block. Commonly, where bedding is present, it shows parallelism with the enclosing beds. Occasionally in the intermediate member of the Canelo Hills Volcanics, blocks of volcanic conglomerate or red siltstone similar to those in the lower member of the Canelo Hills Volcanics are present with the limestone blocks and are also enclosed in volcanic flows.

The "exotic" blocks thus far described were prob­ably positioned by gravity slides over very short distances. Other interpretations exist; it is possible that thrusting of upper Paleozoic sediments took place in the area. Pre­sume ably then, erosion followed leaving only klippen around which the Canelo Hills Volcanics accumulated. This theory does not explain the existance of large blocks throughout the Canelo Hills Volcanics section. Another theory combines sporatic landsliding into the Canelo Hills Volcanics basin

67with rafting of blocks by lava flows (Simons and others, 1966). The first part of the theory is acceptable for consideration; the second part has no proven precedent.

Regional Implications of the Exotic BlocksTwo earlier workers in the Canelo Hills area have

described thrust faults. Feth (1947) , working in the northern Canelo Hills, mapped Permian limestones thrust to the southwest onto Cretaceous (?) redbeds and Tertiary volcanics. The present writer has briefly visited the area and believes that these redbeds and volcanics are the northern equivalent to the lower two members of the Canelo Hills Volcanics. If this is so, exotic blocks may be present and serious doubt can be cast on the thrust fault of Feth. Fenster and klippen could be due to erosion of large exotic blocks enclosed in the Canelo Hills Vol­canics. One would expect these blocks to be brecciated as Feth describes.

Further, a line of exotic blocks could easily be mistaken for outcrops along a single thrust front in this area where outcrops are commonly poor. Simons and others (1966) have mapped a front of blocks along the contact of the Concha Limestone with the Canelo Hills Volcanics a few miles southeast of Feth.

The writer has observed exotic blocks in the northern part of Feth's area. These appear to crop out

68along a normal fault that dips 60° to the southwest. Additional work in the area is suggested.

Cetinay (1967) describes a northeast thrust of Paleozoic rocks onto "Upper Cretaceous" rocks in an area less than two miles north of the immediate area of study. The writer has visited the area; and although exposures are poor, he believes that the basal Canelo Hills Volcanics exist in fault contact with both pre-Triassic rocks and the Cretaceous Bisbee Group. Regardless of the poor expo­sures, the basal Canelo Hills Volcanics are unmistakeably present. Apparently Cetinay believes the large blocks of limestone present in the area of Mesozoic sediments are klippen, cut off from the other pre-Triassic sediments by erosion. An alternate hypothesis to the thrust described by Cetinay is that large gravity-transported blocks of limestone are interbedded with the basal Canelo Hills Volcanics and are today exposed by erosion along a normal fault.

If the exotic block hypothesis presented in the above paragraphs holds up, previous ideas on structural relations may warrant reappraisal elsewhere. This is especially true in places where Paleozoic rocks have been interpreted as thrust onto "Cretaceous (?)" rocks. The existance of exotic blocks interbedded in younger sediments should not be considered unique to the Canelo Hills Vol­canics. Such features are also known in the Tucson

69Mountains and in the Catalina Mountains and are probably more common elsewhere than has previously been supposed.

Late Gravity SlideA single block of the Scherrer and Colina Forma­

tions overlies limestones of the Earp Formation in the SW% of section 12. This block, which caps a small hill, has a thickness of less than 100 feet. The lower contact of the block with the underlying Earp Formation dips gently to the south. Strata of the Earp Formation, on the other hand, dip 40°-45° southwest.

Fossils within the limestone definitely establish the age of the rocks. The presence of the chert-pebble conglomerate of the Earp Formation on the north side of the block proves the age of the underlying limestones.The conglomerate appears to strike under the block, but faulting makes this uncertain. The relationship of the block to the underlying Earp Formation is that of an erosional remnant of a gravity-slide block. This gravity slide must have occurred following tilting of the central Canelo Hills block. No other interpretation will account for the contact relationships. The nearest present-day occurrence of the Scherrer Formation known by the author is six miles northwest in the northern Canelo Hills block. However, Bryant (personal communication) believes that the block could have come from the west, near the crest of the Canelo Hills.

CHAPTER 6

SUMMARY

The retreat of the Permian seaway brought an end to the long period of stability existing in southeastern Arizona. Erosion succeeded the deposition of limestones.If any deformation took place, it must have been slight, as no record of it has been preserved.

During the Late Triassic or Early Jurassic, the Canelo Hills area began to subside and accumulate thick sequences of coarse debris. This debris must have ori­ginated from erosion of a rising highland somewhere in the vicinity of the present-day Huachuca Mountains.Tectonic activity in this area probably gave rise to gravity slides of large limestone slabs into the Canelo Hills basin. Some of these were then enveloped by incoming sediment. Others were present when volcanic flows inter­rupted normal deposition and were hence enclosed by lavas.

The activity that resulted in the accumulation of the thick sequence of volcanic material at the top of the Canelo Hills Volcanics had subsided by Early Cretaceous time. Some erosion of the Volcanics followed, only to be halted by the deposition of the conglomerates, sandstones, and shales of the basal units of the Bisbee Group.

70.

Appendix I.

The classification of limestones used in this report is that proposed by Folk, 1962. The classification is presented as Table 1. The percentage of dolomite fraction was determined by the staining procedure out­lined by Dickson (1965).

Criteria used in the construction of the energy- level diagrams (Figs. 2, 5 and 6) was taken from Plumley and other, (1962) and is presented as Table 2 .

Finally, the terminology used in describing the thickness of stratification in sedimentary rocks was adapted from Ingram (1954) . This classification consti­tutes Table 3.

72

Table 1Classification of Carbonate Rocks

(From Robert L. Folk, 1962)

Limestones, Partly Dolomitized Limestones, and Primary Dolomites (see Notes 1 to G)

Rtplaiement Dolomites7 (V )

| > 1 0 % AllochcmsAlluchemical Rocks (1 and I I )

< 1 0 % Allochcms Microcrystalline Rocks ( I I I )

Sparry Calcite Cement > M ic ro - crystalline Ooze

M atrix

Microcrystalline Ooze M a tr ix

> Sparry Calcite Cement 1-10% Allochcms <1%

Allochcms

Undis­turbed

BiohermRocks

( IV )

Allochem Ghosts N o Allochem Ghosts

Sparry Allo- chcmical Rocks

(I)M icrocrystalline

Alochcmical Rocks(ID

1

Intr

acla

sts

(i)

Intrasparrudite( I i :L r )Intrasparite( Ii:L a )

Intram icrudite* ( I I i : L r ) Intram icrite* (H i: La)

Intraclasts: Intraclast­bearing Micrite* ( I I I i : L r or La)

Finely Crystalline Intraclastic Dol­omite (Vi: DJ)etc.

Medium Crys talline Dolo­mite (V : D t)

1j1

1

' ■ S '

Obsparruditc( Io :L r)Obsparitc(Io :L a )

Oomicrudite*( I Io :L r )Oomicrite"( I Io :L a )

i

Oolites:Oolite-bearing M icrite* ( I I Io : L r or La) .1 E

Coarsely Crxstal- linc Ovlitic Dolomite (Vu:D 5) etc.

Finely Crys­talline Dolo­mite (V : 1)5)

1

i5 s

Biosparruditc ( Ib :L r ) Biospa rite ( Ib : U )

Biomicrudite ( I Ib :L r ) Biomicrite ( I lb : La)

1IFossils: Fossilifcrous M icrite fIJ Ib : Lr, La, or LI)

Mic

rite

(II

Inv

.L);

if

dist

ui

crite

(II

!mX

:L);

if

prim

al

Dol

omic

ritc

(H

im

3

1J 1fW

AphanocrytLalline Bic'genic Dolomite (V b :D l) etc.

5V

1!

Vol

ume

Rat

io r

Fo

ssils

to

Pelle

t 1* Biopelsparitc(Ibp :La )

Biopvlmicrite(H b p :L a )

<

iPellets: Pelletiferous M icrite ( I I Ip : La)

«

Very Finely C ryslalline Pellet Dolomite (V p :D 2) etc.

etc.

& Pelsparite (Ip : La)

Pelmicrite( IIp :L a )

I !

N O T E S TO TA B L E I

i N a m e iam i fvmbcls m the body cf the table refer to limestones. If the me l contains more than 10 per cent replacement dolomite, prefix the term "do],-mitized" to the rock name, and use D L r cr D La for the symbol <e g,, dolomitized intrasparite, Li: D U ) . I f the rock contains more than 10 per cent dolomite of uncertain origin, preftr the term •M-’lomitic’, to^thej r.xk. name, and use dLr or dl.a for the symMI (e g., dolomitic rxlspante, I p : d U ' . I f the rock consists of primary (directly deposited) dolomite, prefix the term ‘‘primary dolomite to

^ TW z\r T1 f z. r iY\M VkzJ 4 * <• r>n m n r\f i n t r** % / r \ • + I T i • i \ Tncfr^r^ af rV m 1C f 11 f (III PH ! I)) t hf t r rm *4 dv 1 ‘)mif TltP 9 1712 V 1 11SCQ.t te rock name, and use Dr or Da for the symbol (e g., primars' dolorr% Upper name in each box refers to calciruditr* (median allochem ‘■ize larger t: an

size and quantity of ooze matrix, cements or terrigenous grains are ignored.* If the rock contains more than 10 ;z r cent terrigenous material, prefix " 'a n d y ,” “ silty,” or “clayey” to the rock name, and

i> dominant (e g., sandy bio^pante, T 'lb '.L a , o,r silty dc-lomitizui pclmi^rite, T : I I p : D U ) . Glauconite, cellophane, chert, pyrite. . . .4 If the rock contains other alk-cherns in figniticant quantities that are not mentioned in the main r«>c k name, these should be prefixed as qualifiers ; 'tee n.ng the main rock narm , f- ro is intrasparite, oolitic pelmi-Tite, pellet if erous ovsparitr, or intraclastic hi1- micrudite). 'This can 1 c sho.s n s> mix li call y as li< b), Iu(p), I Ib h \ respectively.* If the fusils .-ire < f r ith< r unde rm typ^ r r < t.c tyi>e is dominant, this fai t >;i-_ uM U* ^huwn in the rock name te g , ttlecviK'd bioipamudite. erin-ud bioTiicrite). . ,, j* 11 the r... k was ori iri.ii y m. r ' ' r>’ t ih.r.c j,;. J (an be shev n t h a \r reerve'.ah..-- d to micrcspar (5-15 micron, clear can itel the terms “mn. rvspmr:4e, ••, .i..»^*cr«*«jvirite, etc. can s^d in -fend of “ nic nre1' cr ' biomi< rite.”7 b; r. ;fy ( rysf^; vj/r as sho*n in the examples.

mite intram urite , H iiD a ). Instead of “ primary dolomite m icrite” ( I I Im r D ) the term “ dcl-micrite” may l*e used.1.0 mm ); and lower name refers to all rocks with median allochem size smaller than 1.0 mm. Grail

and “ Ts,” “Tz.,” or “ Tc ' to the symbol de^ndingon which or other mc’i'.ifiers may a !^ h-e prefixed.

iers : 't cc ime the it

Table 2Energy Index Classification of Limestones

Basis of interpretation of 1imestonesnuscdain tScecoAstruciion of figures 2,5 and 6.

Limestone Type According to

Energy Index

| Limestone | M inerdogyTexture Fossil Abundance | C n iro rte r iilic Fossils'

F o \n l-A ss jtiU ions I Fossil Fresenotion\ Sub-Types Size Sorting ' Roundness and Complexity

L_

iCaiciteClay (15 10 50% ; D etrital quartz ( < 5 % ) Microcrystalline carbonate (< 0 .06

mm) or any size fossil fragments in a microcrystalline carbonate ma­trix (matrix < 5 0 % )

M a trix — good Fossils—poor

\Barren to moderately fossiliferuus Simple assemblages

| Crnnids; echir.oids; Lryozoans (fragile j bra fit h i ng t y; *:s); solitary’ corals; ost racodes:

thin-s.Viied brarhioj»ods, i>elecyjM>.i>, and ga-trop/ds; Foraminifera; sponge spicules; tubular, er,crusting, and sediment-binding algae; ft-' a! [file ts of bottom scavengers.

Common fovsil associations are crinoM- bryozoa assemblages, bivalve shell assem­blages, Foraminifera assemblages (predomi­nantly planktonic).

M any fossils are whole and unbroken and are not mechanically abraded. Any fragmen­tation of fossil material probably is due to disarticulation upon death, to predatory (boring, ojening, and breaking) activity and scavenger activity, or to solution.

Q U IE T

Deposition in quiet eater

I:Calcite (predominant) Clay ( < 15%)D etrita l quartz (< 5 % )

Original fossil shapes; angular fragments if broken

I .Any size fossil fragments in micro- crystahine matrix (matrix < 5 0 % )

M atrix—good Fossils— moderate to good

i Moderately to abun­dantly fossiliferous Simple assemblages (coquinoid limestone)

IN T E R M IT T E N T L YA G IT A T E D

I IDeposition alternately in agitated water and

H iMicrocrystalline matrix (> 5 0 % ). M i­crograined to medium-grained clas­tic carbonate and terrigenous material M atrix— good

Clastic material— poor to good

Clastic carbonate material subangular to rounded. Roundness of terrig­enous elastics is principally a function of size.Oolites may be pres­ent

Barren to moderately fossiliferous. Moder­ately simple assemblages

Characteristic fossils and fossil associa­tions are similar to Type I limestones.

Fossil materials are more fragmental than those in Type i limestones and also may be more or less rounded by wave action. Scat­tered fragments of fossils from rougher water environments may be present.

H iC a lc ite (p re d o m in a n t)Clay (< 2 5 % )Detrital quartz (< 5 0 % )

M icrocryst.-illfne matrix (> 5 0 % ). Coarse- to very coarse-grained clas­tic carbonate and terrigenous material

in quiet water

I LInterbcdded microcrystalline car­bonate and any size clastic. M icro­scale rhythmic bedding

Sorting pood with­in individual lam­ina

Barren to moderately fossiliferous. Moderately complex assemblages

H i t Micrograined clastic carbonate (< 0 .0 6 mm) predominates M atrix—good

Clastic material— moderate to good

Barren to sparsely fossiliferous Simple assemblages

Echinodcrm, bryozoan, and bivalve shell debris; Foraminifera; encrusting algae.

Common fossil associations are Forami- nifera-abraded bivalve shell fragment assem-

Fossil materials comminuted from larger fossil structures are well abraded by wave and current action.

S L IG H T L YA G IT A T E D

I I IDeposition in slightly agitated water

I I I *Calcite (predominant) D etrita l quartz (up to Very fine-grained clastic carbonate

(0.06 to 0.125m m ) predominates

Clastic material sub­rounded to well rounded.Fine-grained oolites may be present

Barren to moderately fossiliferous Simple assemblages

I I LFine-grained clastic carbonate (0.125 to 0.25 mm) predominates

M atrix— poor Clastic material— moderate to good

Barren to abundantly fossiliferous Simple to moderately complex assemblages

IV i Medium-grained elastic carbonate (0.25 to 0.5 mm) predominates

Moderately to abun­dantly fossiliferous Simple to moderately complex assemblages

Crinoidq echinoids, bryozoans, brachio- pod and pelccypod shell fragments, colonial coral fragments, stromatuporoid fragments (Silurian and Devonian predominantly); tu - bulir algal fragments, colonial algal frag­ments (rare), encrusting algae.

Common fossil associations are similar to associations of Ty|»cs I , I I , and I I I , or they are mixtures of these associations.

Fossil materials are generally broken and abraded.

M O D E R A T E L YA G IT A T E D

. 1YDeposition in moder­ately agitated water

IV *Calcite (predominant) Detrital quartz (up to 50% )

Coarse-grained clastic carbonate (0.5 to 1.0 mm) predominates

M atrix— poor Clastic m a te r ia l- moderate to good

Clastic material sub- rounded to well rounded. Oolites may be present .

IV ,Very coarse-grained clastic carbon­ate (1.0 to 2.0 mm) predominates

Moderately to abun- antly fossiliferous Moderately complex to complex assemblages

S T R O N G L YA G IT A T E D

VDeposition and growth in strongly agitated water

Vi

Calcite (predominant) Clay (< 5 % )Detrital quartz (< 25% )

Gravel-size clastic carbonate (rock fragments and fossil material > 2 .0 mm) predominates

M atrix— poor Clastic m a te r ia l- poor to moderate

Clastic material sub- rounded to well rounded. Pisolites may be present

Sparsely to moderately fossiliferous Complex assemblages

Crinoids; echinoids; encrusting bryozoans: thick-shelled brachiopods, txdecyjxids, and gastropods; colonial coral fragments; stro­ma to poroid fragments (Silurian and Devo­nian predominantly); colonial algal frag­ments; rudistid fragments (Cretaceous pre­dominantly).

Fossil associations are similar to Type IV associations.

Fossil materials are generally broken and abraded.

V,Gravel-size conglomeratic or brec- ciatedcarbonate (> 2 .0 m m ) Tectonic breccias excluded

M atrix— poor Clastic material— poor

Clastic material angular to well rounded

Barren to sparsely fos­siliferousComplex assemblages

V, Calcite Not applicable N o t applicable Not applicable

Abundantly fossiliferous Simple assemblages ffossil colonial growth in place)

Colonial corals, stromatoporoids, colonial algae (principally the Rhodophyta or red algae and some genera of the Cyanophyta or blue-green algae).

75

Table 3

Classification of Thickness of Stratification Units Adapted from Ingram, 1954

MASSIVE

VERY THICK100

tnuooE• H4->£OU£•H

tntno£u• H•£H

THICKcz:.owPQ MEDIUM

THIN

VERY THIN

w<THICK LAMINAE

THIN LAMINAE

76

Measured Sections

Measured sections were chosen on the basis of structural simplicity, exposure and completeness of sec­tion. Sections were measured with a Jacobs staff. With the exception of the generalized Earp section and the Canelo Hills Volcanics section, each interval was sampled and studied, both in hand specimen and thin section.Each unit of the Canelo Hills Volcanics was sampled; however, these were studied under the binocular micro­scope. Selected specimens from the Earp Formation,Canelo Hills Volcanics and the Colina Limestone, which was not measured, were also studied in thin section.

Appendix II.

77

Measured section of the Abrigo Limestone.Location: S%, NE%, NE% of section 7, T22S, RISE. Thissection was measured in the streambed above Rattlesnake Dam by making repeated offsets along beds so as to remain in the streambed.

Upper contact: disconformity with Martin Formation, showsabout 2 feet of relief.

Unit No. Thickness in feet.12 Quartzite, grayish orange (10YR 7/4).

Quartz grains are 0.75 mm dia., well sorted and well rounded. Sand makes up 40 to 80% of rock in any one thin section. Unit has finely crystalline intraclastic dolomite matrix. Some sparry calcite is present in the form of unreplaced intraclasts 2 - 3 mm dia.Unit forms ledge. 2%

11 Dolomite, light red (5R 6/6), finelycrystalline intraclastic, grades upwardinto quartzite. Sparry calcite is presentonly in trace amounts. Unit is thick bedded. 7

Section 1.

78

Fault, left-lateral displacement of a few feet.10 Intrasparrudite, laminated with limy-

quartzite. Laminae give rock a dis­tinctive color banding alternating between moderate reddish orange (10R 6/6) to medium light gray (N6).Ferroan calcite intraclasts are 1 - 2 mm dia. Quartz grains are less than 0.25 mm dia., poorly sorted, subrounded.Laminae are 1 - 3 mm thick. Some cross­bedding is visable on weathered surface.Unit forms ledge. 4%

9 Intrasparrudite, light gray (N7). Intra­clasts are less than 0.50 mm dia. Unit is thin bedded, cliff-forming. 16%

8 Dolomitic micrite, grayish red (10R 4/2).Dolomite is 10 - 15% of rock. Limestone is hard and massive. 21

7 Covered, probably same as unit 8 . 56 Intrasparenite, grayish orange (10YR 7/4).

Limestone is massive with veinlets of sparry calcite.

Unit No. Thickness in feet.

7

79

5 Pelmicrite, weathers dark yellowish brown (10YR 4/2). Pellets are 0.50- 1.25 mm in dia. and composed of hematite when fresh but limonite close to rock surface. Pellets appear to have a clastic (?) grain in center.A heavy limonite stain is on surface, granular appearance. Unit is thinly bedded with a few blue-gray clay beds. 31

4 Intrasparenite, medium light gray (N6),lightly stained by limonite, thinlybedded, forms ledge. 5%

3 Intrasparlutite, moderate reddish orange(10R 6/6) , set in micrite. Unit is medium bedded, forms blocky ledges. 32

2 Micrite with interlaminated silt,grayish orange (10YR 7/4). Silt is composed mainly of subrounded quartz.Laminae are in beds 1 - 3" thick.Unit has some cross-bedding. 2h

1 Covered. 1Fault places Abrigo Limestone in contact with Tertiary conglomerates and gravels.Thickness of Abrigo Limestone. 158

Unit No. Thickness in feet.

80

Measured section of the Martin Formation.Location: Center, NE% section 7, T22S, RISE, measuredalong gentle slope on the flank of Escabrosa Hill.

Upper contact: contact with Escabrosa Limestone arbi­trarily put at top of light colored dolomite sequence. Overlying Escabrosa Limestone is coarse-grained, massive, dark in color. Contact is slightly irregular, often is a strongly leached zone.

Unit No. Thickness in feet.30 Dolomite, light gray (N7) alternating

with medium light gray (N6), medium crystalline intraclastic. Grain size decreases downward to finely crystalline intraclastic dolomite at base. 79

29 Dolomite, medium gray (N5) , finelycrystalline intraclastic. Contains 10% clasts less than 1 mm dia. and 5% sparry calcite. Bedding is thick, forms ledge. 6

28 Dolomite, brownish gray (SYR 4/1) , finely crystalline intraclastic. Intraclasts range up to 0.50 mm. Unit is mainly

Section 2.

81

28 Continued:covered, appears to be medium to thin bedded.

27 Dolomite, similar to unit 25.26 Covered.25 Dolomite, brownish gray (SYR 4/1),

finely crystalline sandy. Sand is very fine grained (less than 0.15 mm dia.) well sorted, subangular to subround. Unit is thin bedded.

24 Covered.23 Dolomite, dark gray (N3), finely

crystalline intraclastic. Intra­clasts are 0.50 - 1.00 mm dia., consisting of rhombohedral crystals of calcite. Unit is medium bedded, forms step.

22 Covered, float is light colored dolomite.21 Dolomite, brownish gray (SYR 4/1),

weathers light gray (N7), finely crystalline, massive bedding.

20 Covered.19 Dolomite, brownish gray (SYR 6/1),

weathers mottled pink and greenish

Unit No. Thickness in

302

9

feet.

114

529

15%2

82

19 Continued:gray colors, very finely crystalline.Thick bedded with chert nodules of less than 2" dia. Many veins ofdark calcite 3

Fault (?)18 Limestone breccia (?) or conglomerate

(?): Unit does not appear to continuealong strike. Limestone fragments range in size up to 2" dia. Probably a breccia. 3%

17 Intramicrenite, light olive black (5Y 3/1) , Intraclasts are less than 1 mm dia. and consist of intrasparudite and pellets. Clastic material ranges in size from silt to very fine sand.They are poorly sorted and subrounded.Intraclasts are moderately sorted and subrounded. 5

16 Covered, probably same as unit 15.15 Dolomitic Orthoquartzite, dark yellowish

brown (10YR 4/2). Sand grains range from 0.07 - 0.15 mm. They are sub- angular to subrounded. Unit is thick

Unit No. Thickness in feet.

83

15 Continued:bedded. Sample contains abundant shell debris into which sand grains have grown during diagenesis. Shell debris is composed of calcite. 3

14 Mostly covered, float suggests sandstonepoorly consolidated. 11

13 Limy sandstone, pale red (5R 6/6), grains range from 0.07 to 0.20 mm., poorly sorted, subangular quartz sand. Calcite cement. Thick to thinly laminated. Contains higher proportion of large grains and cal­careous material than unit 15. 2

12 Limy orthoquartzite, pinkish gray(SYR 8/1) , coarse grained, moderately sorted, rounded quartz grains. Some intraclasts of limestone present.Thickly laminated. 3%

11 Orthoquartzite, pale reddish brown (10R 5/4) ; sand grains range from 0.06 to 0.30 mm. They are poorlysorted, subangular. Unit forms flats. 4%

Unit No. Thickness in feet.

84

10 Intrasparlutite, medium dark gray (N4),Intraclasts are less than 0.02 mm; they are closely packed to form a mosaic pattern. Well sorted, subangular,thick bedded, poorly exposed unit. 6%

9 Covered. 38 Dolomite, moderate reddish brown

(10R 4/6), medium crystalline intraclastic. Intraclasts are less than 0.30 mm, poorly sorted, subangular. Less than 5% angular quartz present as scattered 0.20 mm dia. grains. Medium bedded. 1%

7 Covered, probably same as unit 6 . 26 Ferroan intrasparenite, pale reddish

brown (10R 4/6); sand is 0.15 mm dia., well sorted, subangular, comprises 20% of rock. Intraclastics are angular sparry calcite and comprise 40% of rock. Intraclastics and quartz grains are set in micro­crystalline ooze. Rock forms flat slope; contains many sparry calcite veins. 1%

Unit N o . Thickness in feet.

Unit No.85

Thickness in feet.5 Intrasparenite, mottled brownish

gray (SYR 4/1) , coarse clasts of sparry calcite, moderately sorted, rounded and held in micrite matrix.Less than 5% fine grained quartz.Thick, massive bedded. 16%

4 Intrasparudinite, light grayishwhite (N8) , medium bedded. 2%

3 Covered, probably more of unit 2. 92 Dolomitic intrasparudinite, moderate

brown (SYR 3/4) , weathers pale yellowish brown; fine grained, moderately sorted, angular quartz grains constitute 25% of rock and are cemented by finely crystalline spar. This also cements irregularly shaped intraclasts up to 4 - 5 mm dia.Unit is thinly bedded to laminated. 2

1 Covered. h

Thickness of Martin Formation 278%

Contact with top of Abrigo Limestone. Attitude of Martin Formation is N2(PW, 32°SW; attitude of underlying Abrigo Limestone is N33°W, 34°SW. Top of Abrigo is quartzite ledge showing a slightly irregular surface.

86

Section 3.

Measured section of the Escabrosa Limestone.Location: section 7, T22S, RISE, measured alongeastern spur and the crest of Escabrosa Hill.

Upper contact: Horquilla Limestone, light colored,fine grained, medium bedded limestone. Contact with the underlying Escabrosa Limestone is along an erosional disconformity. In most areas, a red limestone conglo­merate lies 50 feet above the contact within the Horquilla Limestone. A few feet above that there is a prominant Neospirifer zone.

The erosional disconformity at the base of the Hor­quilla Limestone is readily recognizable by a thick bed (38.5*) of red chert. This bed is commonly poorly exposed so that the thickness given here may include some limestones buried by cherty rubble.

Unit No. Thickness in feet.28 Intrasparenite, similar to unit 26. 5527 Intrasparenite, moderate yellowish

brown (10YR 5/4), weathers pink; clasts are well sorted, angular sparry calcite set in micrite ooze. Thick bedding. 5

87

26 Intrasparenite and Pelsparite, light gray (N7); clasts are poorly sorted, angular to subround, sparry calcite ranging up to 1 mm in dia. Pellets are 0.30 to 1.00 mm in dia. Cemented by sparry calcite. Pelsparite becomes dominant near base of the unit. Rock is finely laminated, crinoidal, and poorly exposed. 70

25 Intrasparenite, similar to unit 23,thick bedding. 7

24 Intrasparenite, light gray (N8). Clastsare less than 0.20 mm dia., poorly sorted, and angular ferroan sparry calcite in micrite matrix. Thick bedding. 7

23 Intrasparenite, dark gray (N3), clastsare less than 0.50 mm dia., poorly sorted, subrounded, sparry calcite. Matrix is micrite. Thick bedding. Contains many large rugosa corals. Syringapora sp. found 251 from base. 33

22 Intrasparenite, similar to unit 20 but contains a pale brown one foot bed of intraclast-bearing micrite. Clasts comprise

Unit No. Thickness in feet.

88

22 Continued:less than 10% of rock. They are angular and about 0.90 mm in dia. Contains large rugosa corals and Lithostrontenella sp.Forms gentle slope. 61

21 Covered. 1220 Intrasparenite, medium brownish gray

(SYR 5/1). Clasts are 0.30 mm dia. and are poorly sorted, angular. Interval contains a few 1 - 2" chert nodules.Forms step. 5

All above units measured on near dip-slope.19 Pelsparenite, medium gray (NS), and

Pelletiferous intrasparudite, light gray (N7). Base is intrasparudite with clasts ranging up to 2 mm (most less) and a few 0.30 pellets in micrite.Upper part is Pelsparenite. Pellets are 0.20 - 0.30 mm dia., in laminae.Unit forms gentle slope. Offset 115 feet north along base of over-lying bed. 104*5

18 Dolomitic micrite, medium dark gray(NS), steep slope-forming limestone.Rugosas present. 82*5

Unit No. Thickness in feet.

89

17 Intrasparenite, dark gray (N4).Intraclasts are 0.15 - 0.50 mm dia., well rounded, and composed mainly of micrite cemented by sparry calcite. Thick bedded, cliff­forming. Uppermost bed contains Syringopora sp. The rest of the bed is conspicuously non-fossiliferous and non-cherty. Offset 250 north along top of this bed. 24

16 Intrasparlutite, grayish brown(SYR 3/2). Similar to unit 17 except in grain size. Interval is mostly covered. Thin bedding with 1 - 2M black chert nodules. 16

15 Intrasparenite, same as unit 10.Fossils present are Lithostronella sp.,Syringopora sp., and large rugosa corals. 6

14 Fossiliferous intrasparenite, weathers medium gray (N5). Clasts are poorly sorted and angular. Sample is actually coral biolithite. Fossils present are Lithostronella sp., Syringopora sp.,

Unit No. Thickness in feet.

and large rugosa corals. Many black

90

14 Continued:chert nodules 1 - 2 ’ are present.

13 Micrite, grayish red (5R 4/2), contains a few pellets 0.05 mm in dia. Unit is poorly exposed.

12 Interbedded dolomite and intrasparenite, medium olive gray (5Y 5/1) , finely crystalline, distinctively thinly laminated. Unit contains rugosa corals.

11 Intrasparenite, brownish gray (SYR 4/1) , intraclasts are moderately sorted, rounded, and cemented in micrite. Unit is mostly covered.

10 Intrasparenite, grayish black (N2).Clasts are about 0.12 mm dia., poorly sorted and angular. Unit forms gentle cliff and is medium-thick bedded.Upper 7' has very abundant rugosa and Lithostruntella sp. corals.

9 Intrasparenite, medium gray (NS); clasts are about 0.12 mm dia. and subrounded.Unit forms step with medium bedding.

8 Similar to unit 7. Contains large rugosa corals and small crinoid plates (1/8").Offset 130 feet north along base.

Unit N o . Thickness in

5%

7

Ik

8

21

2k

feet.

5

Unit No.7 Dolomite, pinkish gray (SYR 8/1),

medium crystalline, intraclastic.Intraclasts range up to 1.00 mm dia. and are poorly sorted, angular. 2

6 Dolomite, medium gray (NS), finelycrystalline, intraclastic. Most clasts are 0.25 mm.; some reach 0.80 mm.Medium bedded unit contains a few quartz geodes. 3

5 Intrasparudite, same as unit 3 withrugosa corals. 8

4 Dolomite, light gray (N7) , same as unit 6 . 33 Intrasparudite, light gray (N7). Clasts

range up to 2.5 mm dia., are poorly sorted, subrounded to angular. Unit is thick bedded with sugary texture on broken surface. 3

2 Pelrenite, medium gray (NS) with rounded intraclasts 1 - 2 mm in dia. Pellets are of micrite. Intraclasts are micrite with very fine sand. Matrix is sparry calcite. At 20’ above base, there are very abundant and large colonies of Syringopora sp. (6M dia.) and rugosa

91

Thickness in feet.

corals 3 - 4" long. Chert nodules

92

2 Continued:and quartz geodes are abundant from 181 to 251 above base. Above 50 * from base, three breccia zones indicate faulting thought to be minor.

1 Fossiliferous pelletiferous intrasparudite, light gray (N7). Pellets are 0.20 mm.; clasts are 1 - 2 mm dia. Pellets are composed of micrite. Clasts are rounded and composed of pellets and sparry calcite and some fossil debris. Unit is massive.Upper 2$5 feet are covered.

Total thickness of Escabrosa Limestone Contact at the top of Martin Formation is gradational; it is picked as the point where massive limestones are in contact with thin to medium bedded dolomites.

9 Dolomite, light olive gray (5Y 6/1) , finely crystalline, intraclastic. Clasts are about 0.15 mm dia., poorly sorted and angular.Unit forms step; weathered surface has raspy texture.

8 Dolomite, light brownish gray (SYR 6/1) , same as unit 9, thick bedded.

Unit No. Thickness in feet.

46%

16%516%

17%

93

Unit No. Thickness in feet.7 Dolomite, brownish gray (SYR 5/1),

finely crystalline, medium bedded, forms slope. Sk

6 Dolomite, light brownish gray (SYR 6/1),same as unit 9; medium bedded, step forming. 2h

5 Dolomite, same as unit 3. 94 Covered. 43 Dolomite, light olive gray (5Y 6/1)

coarsely crystalline, thin to medium bedded. 7h

Fault displacement unknown (probably minor).2 Limestone fault breccia. 21 Sandy intrasparenite, moderate brown

(SYR 3/4). Quartz grains range in size up to 0.15 mm dia. and are medium sorted, subangular to subround. Clasts of sparry calcite range up to 0.20 mm dia., angular. Unit is laminated. 6

Thickness of partial section of Martin Formation 60

94

Section 4.

Measured section of the Earp Formation.Location: SE%, SE% of section 12, T22S, RISE.

Unit No, Thickness in feet.Top of exposure, not top of section.

26 Fossiliferous micrite, brownish gray (SYR 4/1), massive bedding, jointed.Fetrid odor when broken. There are many broken Echinoid spines replaced by sparry calcite. 20

25 Fossiliferous micrite, pale brown (SYR 5/2), arenaceous, grains range up to 0.20 mm dia., are angular. A few broken echinoid spines are replaced by sparry calcite. Rock forms a depression running along top of ridge. 20

24 Limestone, dark gray aphanitic. Mudclasts weather out along bedding planes. Unit is similar to unit 15. 62

23 Limestone, dark pink color, arenaceous,similar to unit 2. 2

22 Covered, probably same as unit 23 above. 321 Limestone, black (Nl), weathers to a

light blue gray, is dolomitic. 85

Unit No.95

Thickness in feet.20 Dolomite, light brown (SYR 5/6),

finely crystalline, arenaceous, laminated. Quartz grains are moderately well sorted, angular, and imbricated along laminae. Some cross bedding is present. 2

19 Covered. 2018 Limestone, light gray color. Leaching

has given this rock a vugular appearance.The lower 7 feet are covered. 23

17 Dolomite, light gray color, aphanitictexture. 5

16 Dolomite, pale yellowish brown (10YR 6/2),finely crystalline intraclastic. Clasts are up to 2 mm and are angular. Many vugs are present filled with secondary yellow calcite. Bryzoans are present.Unit appears massive, but is sometimes laminated in thin section. 52

15 Intrasparenite, dark gray (N3) ; mosaicof crystalline calcite with 5% sand grains. Quartz grains range to 1.0 mm, many show recrystallization. Two one- foot beds of laminated, finely crystalline,

96Unit No. Thickness in feet.

15 Continued:moderate brownish gray (SYR 6/1) dolomite appear 12 feet and 82 feet from top. Intrasparenite is thick bedded at base but becomes mediumbedded 15 - 20 feet from top. 134

14 Dolomite, brown, finely laminated. 213 Covered. 2012 Intrasparenite, similar to unit 15 but

mainly covered. 6811 Dolomite, pinkish gray, limy, finely

laminated. 710 Covered. 59 Intrasparenite, similar to unit 15. 108 Dolomite, same as unit 14. 47 Limestone, black, aphanitic. 86 Dolomite, dark reddish brown (10YR 3/4)

at top, yellowish gray (5Y 8/1) at base; arenaceous and intraclastic; medium cry­stalline. Clasts are 1 - 2 mm dia. oriented along fine laminations. Sand is quartz, fine grained, subangular, makes up to 15% of rock. 6

5 Limestone, black. 5Dolomite, same as unit 14. 44

3 Covered.2 Dolomite, mottled moderate yellowish

brown (10YR 5/4), arenaceous, intra- clastic, medium crystalline, laminated.Similar to unit 6. Quartz grains make up 40% of rock. Units 2 through 6 appear to be one unit that shows decreasing sand content upwards.

1 Conglomerate, weathers to pale yellowish brown (10YR 6/2) . Rounded pebbles of red, gray, and white chert up to 1 inch in size are cemented by intrasparenite. Unit becomes finer 5 * above base and gives way to pink dolomite.

Partial thickness of the Earp Formation

Measured section starts in gully in the NE%, SE%,SE% of section 12, at an elevation of 5,500 feet.

Undetected faulting probably exists accounting for the excessive thickness (when compared to other strati­graphic sections) of the Earp Formation above the chert pebble conglomerate. Units 1 - 2 1 fall within the middle terrigenous member of the Earp Formation.

Unit No. Thickness in10

10

5

574

97feet.

98

Section 5.

Measured section of the Canelo Hills Volcanics Location: NW corner, SE% section 13, T22S, R17E. Sectionbegins in stream bed.

Unit No. Thickness in feet.Top of exposure, not top of section.

30 Rhyolite tuff, pale red (5R 6/2) in the lower part, grades to light brownish gray (SYR 6/1) at top. Rock fragments up to 3 mm consisting of feldspar and quartz with minor biotite. Unit has a welded appearance in thin section. 242

29 Conglomerate and sandstone. Conglomerate fragments are of volcanic rocks and chert pebbles. Interbeds of sandstone predomi­nant in the upper 2 feet. 6

28 Arkose, badly weathered and soft. 5%27 Conglomerate, similar to unit 25. 326 Pebbly arkosic sandstone, moderate red

(SR 5/4) , medium to fine grained sand with a few chert pebbles 1" dia. 5%

25 Conglomerate, grayish red (5R 4/2).Rock fragments consist of angular limestone, chert and rhyolite pebbles ranging from k - 2" in dia.

24 Sandstone, pale reddish brown (10R 5/4), medium grained, moderately sorted, subrounded quartz and chert grains.Thick bedded unit; lower part is partly covered, upper part forms a ledge. A bed of pebble conglomerate is present 15* from bottom contact.

23 Conglomerate, similar to unit 16 but with rhyolite pebbles predominating; several thin arkose beds are present; forms ledge.

22 Arkose and pebbly arkose, pale red,(10R 6/2). Beds are 3 - 4 feet thick and form ledges.

21 Covered, float is chert, rhyoliteconglomerate. Pebbles range from 1/4 to 3/4 inches in dia.

20 Arkose, pale reddish brown (10R 5/4),medium grained, fair sorting, subangular, thin bedded, forms ledge.

Unit No. Thickness in

99

feet.

7

43

22

22

16%

2

100

19 Covered, same as unit 18 (?). 8^18 Sandstone, pale red (10R 6/2), weathers

orange (10R 5/6); fine grained, well sorted, subrounded quartz and chert grains. Unit is poorly exposed. lh

17 Covered. 1616 Conglomerate, grayish red (5R 4/2) .

Pebbles range from 1/8 to 1 inch dia.; chert and rhyolite pebbles predominate over limestone pebbles. Matrix is medium sorted, subrounded quartz and chert coarse grained sand. 14

15 Covered, float is similar to unit 14. 27%

14 Arkose, pebbly, similar to unit 7. 213 Limestone conglomerate, similar to unit

3, forms steps. 3712 Arkose, pale reddish brown (10R 5/4),

limy, pebbly, similar to unit 7;poorly exposed. 2%

11 Limestone conglomerate, similar to unit3, becomes more coarse at the top. 5%

10 Rhyolite flow, light grayish purple (5P 5/2), vesicular, well developed flow banding, covered at base. 126$$

Unit No. Thickness in feet.

Unit No.

101

Thickness in feet.9 Limestone conglomerate, poorly-

exposed, appears to be similar to unit 2.

8 Covered, float is rhyolite similar to unit 5.

7 Arkose, pale red (5R 6/2), fine grained, poorly sorted, subrounded grains.

6 Covered.5 Rhyolite flow. Color at base is light

brownish gray (SYR 6/1) , becomes light gray (N7) at top. Vesicular, flow banding and cleavage parallel lower contact.

4 Covered.3 Conglomerate, pale red (SR 6/2), fragments

are mainly chert but a few of limestone are present. Pebbles are angular, mostly less than 1". A few fragments exceed 3". Matrix is sparry calcite, quartz and euhedral grains of hematite, well consolidated. Unit is medium to thin bedded, forms ledge.

2 Limestone conglomerate, fragments range in diameter from 1/8 inch to 5 feet plus. Vericolored chert and rhyolite pebbles

llh

15

32

934

2

102

Unit No Thickness in feet2 Continued:

are equally abundant. All fragments are angular. Matrix is poorly sorted, sub- angular quartz sand. Unit has massive bedding, forms a poorly exposed terrace. Elsewhere this unit contains exotic blocks of limestone up to 4,000 feet long. Some large, poorly exposed blocks along this section are oriented parallel to bedding.

Fault--downdrops Canelo Hills Volcanics against Colina Limestone.

1 Rhyolite dike, vertical flow banding, brownish color. Dike was intruded

Total thickness of Canelo Hills Volcanics not

Estimated 1,420

along fault Estimated 50

including unit 1 2,182

Appendix III.

Fauna of the Naco Group within the East-Central Canelo Hills.

Horquilla Limestone Spiriferina sp.Spirifer rockymontanus Composita argentea Composita subtilita Composita sp.Neospirifer goreii (?) Composita ovata Plocezyga sp. (?) Phricodothyris sp. Chaetetes favosus Lophophy1lidium sp.

Also:Fusilinid

Earp Formation Composita sp.Wellerella sp.Worthenia sp.Spirifer occiduus Composita argenta Spirifer rockymontanus (?)

Also:Echinoids and Plecypods

Colina Limestone Polyporia sp.Derbyia sp.Dictyoclostus sp. Composita sp.Meeke11a sp. Omphalatrochus sp.

Also:Crinoids and Echinoids

1()5

REFERENCES

Alexis, Carl 0., 1949, The geology of the northern partof the Huachuca Mountains, Arizona: Ph. D. thesis,University of Arizona. 74 p.

Baker, R. C., 1962, The geology and ore deposits of the southeast portion of the Patagonia Mountains,Santa Cruz County, Arizona: Ph. D. thesis.University of Michigan.

Bryant, Donald L., 1955, Stratigraphy of the Permian System in southern Arizona: Ph. D. thesis.University of Arizona. 209 p.

Cetinay, H. Turgut, 1967, The geology of the eastern end of the Canelo Hills, Santa Cruz County, Arizona:M. S. thesis, University of Arizona.

Cooper, John R., 1959, Some geologic features of theDragoon quadrangle Arizona: in Ariz. Geol. Soc.,Guidebook II, pp. 139-144.

, 1960, Reconnaissance map of the Willcox, Fisher Hills, Cochise and Dos Cabezas quadrangles, Cochise and Graham Counties, Arizona: U . S. Geol.Survey Mineral Investigations Field Studies Map MF-231.

____________ __, and Silver, Leon T ., 1964, Geology andore deposits of the Dragoon quadrangle, Cochise County, Arizona: U. S. Geol. Survey Prof. Paper416. 196 p.

Dickson, J. A. D., 1965, A modified staining techniquefor carbonates in thin section: iji Nature, Feb. 6,1965, p. 587.

Drewes, Harald, 1966, Road log for southern Santa Rita Mountains, U. S. Geol. Survey open file report.

Dubin, David J., 1964, Fusulinid fauna from the type areaof the Earp Formation, Permo-Pennsylvanian, Cochise County, Arizona: M. S. thesis, University ofArizona. 102 p.

104

105

Feth, John H., 1947, The geology of the northern CaneloHills, Santa Cruz County, Arizona: Ph. D. thesis,University of Arizona. 150 p.

Folk, Robert L., 1962, Spectral subdivision of limestone types: in Classification of Carbonate Rocks,a symposium, Memoir 1, Amer. Assoc. Petrol. Geol., pp. 62-84.

Gilluly, James, 1956, General geology of central Cochise County, Arizona: U. S. Geol. Survey Prof. Paper281. 169 p.

________ , Cooper, John R., and Williams, James S. ,1954,Late Paleozoic stratigraphy of central Cochise County, Arizona: U . S. Geol. SurveyProf. Paper 266. 49 p.

Hamblin, W. K., 1956, Origin of "Reverse Drag" on the downthrown side of normal faults: Geol. Soc.America, Bull., Vol. 76, pp. 1145-1164.

Hayes, Philip T., Simmons, Frank S., and Raup, Robert B., 1965, Lower Mesozoic extrusive rocks in south­eastern Arizona--The Canelo Hills Volcanics:U. S. Geol. Survey, Bull. 1194-M. 9 p.

Ingram, Roy L., 1954 , Terminology for the thickness of stratification and parting units in sedimentary rocks: Geol. Soc. America, Bull., Vol 65,pp. 937-938.

Luepke, Gretchen, 1967 , Petrology and stratigraphy of the Scherrer Formation (Permian) in Cochise County, Arizona: M. S. thesis. University of Arizona.52 p.

Plumley, W. J., Risley, G. A., Graves, R. W. Jr., and Kaley, M. E., 1962, Energy index for limestone interpretation and classification: in Classifi­cation of Carbonate Rocks, a symposium, Memoir 1, Amer. Assoc. Petrol. Geol., pp. 85-107.

Ransome, F . L., 1904, Description of the Bisbee quadrangle, Arizona: U. S. Geol. Survey, Folio 112.

Rea, David, 1967, Stratigraphy of the red-chert pebble conglomerate in the Earp Formation, southeast Arizona: M. S. thesis, University of Arizona.

106Schrader, F . C., 1915, Mineral deposits of the Santa Rita

and Patagonia Mountains, Arizona, with contributions by James M. Hill: U . S. Geol. Survey Bull. 582.373 p .

Simons, Frank S., Raup, Robert B., Hayes, Philip T.,and Drewes, Harald, 1966, Exotic blocks and coarse breccias in Mesozoic volcanic rocks of southeastern Arizona: U. S. Geol. Survey Prof. Paper 550-D,p p . 1 2 - 2 2 .

Stoyanow, A. A., 1936, Correlation of Arizona Paleozoic formations: Geol. Soc. America, Bull., Vol. 47,pp. 459-540.

Wanless, H. R., 1949, Letter and measured sections to E. D. Wilson, August 25, 1949: in Open Files, ArizonaBureau of Mines.

Weber, Robert II., 1950, The geology of the east-centralportion of the Huachuca Mountains, Arizona: M. S.thesis, University of Arizona. 191 p.

Wilson, E. D., and Moore, R. T., 1959, Structure of Basin and Range Province in Arizona: Ariz. Geol. Soc.,Guidebook II, pp. 89-105.

PLATE I

/

ot the

EAST-CENTRAL CANELO HILLS SANTA CRUZ COUNTY, ARIZONA

Index map showingapprox imate locat i on o f mapped area Base map from

G e o l o g y by p Paul Denney , 19 6 7 U. S Geol. Survey 7.5 min. O'Donnell Canyon Quadrangle

S c a l e I 2 4 0 0 0l/‘ l miley 2

C o n t o u r i n t e r va l 2 5 feet d a t u m is nnean sea level

Explanation

I g n e o u san d

Se dimentory rocks

| i Oal | Al luv ium

I t 1o ; tqc Grovels, conglomerates,

i f■TJ

^ T K cT Iand lake beds

Smoke Mtn. d i ke1 \ i / - 1Conelo H i l l s Vol comcs i n te rm ed ia te member

Conelo H i l l s Volcomcs basal member

S c h e r r e r Fo rm ation

Col ino Limestone

Eorp Fm , w i t h c h e r t - pebb le cong lomera te

H o r q u i l i a L imestone

E s c o b r o s o Limestone

Mart in Format ion

A b r i g o Limestone

Geol ogic _symbols

C on toc tD as he d where approximatel y located

____£D

F a u l t , sh o w i n g d ipD o t t e d w h e r e i n f e r r e d , dashed w he re

a p p r o x i m a t e l y l o c a t e d D , downthrown s ide; U, up thrown s i d e

F a u l t , c o n c e a l e d

i6Beading

90V e r t i c a l b e d d i n g , top o f beds on south

H o r i z o n t a l b e d d i n g

76*"O v e r t u r n e d b e d d i n g

. -‘2.U n c e r t a i n bedd ing

F l ow bonding

Anticline axis

Sync l i ne axis

i ____*: Kes r f m o n c 11 r P H

Cul ture s y mbol s

i n t e r m i t t e n t s t ream

^L i g h t —duty rood

U n i m p r o v e d rood

aR e s e r v o i r

W i nd m i l l

13°

A p p r o x i m a t e mean d e c l i n a t i o n , 19 5 8

zff 7 f/

P L A T E 2

section 12 section

' PlPe

r ' p i p #

V'Me

l,\ &

PIP#

section 13

Horizontal scale I = 1000 Vertical scale I "= 1000"

All baselines ore 5 4 0 0 ' above sea level.

Not# See Plate I for explanationOnd location of geologic sectionsPlate

Geologic Cross- Sections of the East-Central Canelo Hillsl o o k i n g IN22° W

TrVcvb

G e o l o g y by P. P a u l Denney

1 9 6 7TrJcvr Jcwb